static VALUE
rb_mod_s_constants(int argc, VALUE *argv, VALUE mod)
{
    const rb_cref_t *cref = rb_vm_cref();
    VALUE klass;
    VALUE cbase = 0;
    void *data = 0;

    if (argc > 0 || mod != rb_cModule) {
        return rb_mod_constants(argc, argv, mod);
    }

    while (cref) {
        klass = CREF_CLASS(cref);
        if (!CREF_PUSHED_BY_EVAL(cref) &&
            !NIL_P(klass)) {
            data = rb_mod_const_at(CREF_CLASS(cref), data);
            if (!cbase) {
                cbase = klass;
            }
        }
        cref = CREF_NEXT(cref);
    }

    if (cbase) {
        data = rb_mod_const_of(cbase, data);
    }
    return rb_const_list(data);
}

In the first form, returns an array of the names of all constants accessible from the point of call. This list includes the names of all modules and classes defined in the global scope.

Module.constants.first(4)
   # => [:ARGF, :ARGV, :ArgumentError, :Array]

Module.constants.include?(:SEEK_SET)   # => false

class IO
  Module.constants.include?(:SEEK_SET) # => true
end

The second form calls the instance method constants.

static VALUE
rb_mod_nesting(VALUE _)
{
    VALUE ary = rb_ary_new();
    const rb_cref_t *cref = rb_vm_cref();

    while (cref && CREF_NEXT(cref)) {
        VALUE klass = CREF_CLASS(cref);
        if (!CREF_PUSHED_BY_EVAL(cref) &&
            !NIL_P(klass)) {
            rb_ary_push(ary, klass);
        }
        cref = CREF_NEXT(cref);
    }
    return ary;
}

Returns nested module as an array of Module objects:

module M0
  def self.speak = Module.nesting
  module M1
    def self.speak = Module.nesting
    module M2
      def self.speak = Module.nesting
    end
  end
end
M0.speak             # => [M0]
M0.speak.first.class # => Module
M0::M1.speak         # => [M0::M1, M0]
M0::M1::M2.speak     # => [M0::M1::M2, M0::M1, M0]

static VALUE
rb_mod_initialize(VALUE module)
{
    return rb_mod_initialize_exec(module);
}

Returns a new anonymous module.

The module may be assigned to a name, which should be a constant name in capitalized camel case (e.g., MyModule, not MY_MODULE).

With no block given, returns the new module.

MyModule = Module.new
MyModule.class # => Module
MyModule.name  # => "MyModule"

With a block given, calls the block with the new (not yet named) module:

MyModule = Module.new {|m| p [m.class, m.name] }
# => MyModule
MyModule.class # => Module
MyModule.name  # => "MyModule"

Output (from the block):

[Module, nil]

The block may define methods and constants for the module:

MyModule = Module.new do |m|
  MY_CONSTANT = "#{MyModule} constant value"
  def self.method1 = "#{MyModule} first method (singleton)"
  def method2 =      "#{MyModule} Second method (instance)"
end
MyModule.method1 # => "MyModule first method (singleton)"
class Foo
  include MyModule
  def speak
    MY_CONSTANT
  end
end
foo = Foo.new
foo.method2      # => "MyModule Second method (instance)"
foo.speak
# => "MyModule constant value"

static VALUE
rb_mod_s_used_modules(VALUE _)
{
    const rb_cref_t *cref = rb_vm_cref();
    VALUE ary = rb_ary_new();

    while (cref) {
        if (!NIL_P(CREF_REFINEMENTS(cref))) {
            rb_hash_foreach(CREF_REFINEMENTS(cref), used_modules_i, ary);
        }
        cref = CREF_NEXT(cref);
    }

    return rb_funcall(ary, rb_intern("uniq"), 0);
}

Returns an array of all modules used in the current scope. The ordering of modules in the resulting array is not defined.

module A
  refine Object do
  end
end

module B
  refine Object do
  end
end

using A
using B
p Module.used_modules

produces:

[B, A]

static VALUE
rb_mod_s_used_refinements(VALUE _)
{
    const rb_cref_t *cref = rb_vm_cref();
    VALUE ary = rb_ary_new();

    while (cref) {
        if (!NIL_P(CREF_REFINEMENTS(cref))) {
            rb_hash_foreach(CREF_REFINEMENTS(cref), used_refinements_i, ary);
        }
        cref = CREF_NEXT(cref);
    }

    return ary;
}

Returns an array of all modules used in the current scope. The ordering of modules in the resulting array is not defined.

module A
  refine Object do
  end
end

module B
  refine Object do
  end
end

using A
using B
p Module.used_refinements

produces:

[#<refinement:Object@B>, #<refinement:Object@A>]

static VALUE
rb_mod_lt(VALUE mod, VALUE arg)
{
    if (mod == arg) return Qfalse;
    return rb_class_inherited_p(mod, arg);
}

Returns true if self is a descendant of other (self is a subclass of other or self includes other):

Float < Numeric    # => true
Array < Enumerable # => true

Returns false if self is an ancestor of other (self is a superclass of other or self is included in other) or if self is the same as other:

Numeric < Float    # => false
Enumerable < Array # => false
Float < Float      # => false

Returns nil if there is no relationship between the two:

Float < Hash        # => nil
Enumerable < String # => nil

VALUE
rb_class_inherited_p(VALUE mod, VALUE arg)
{
    if (mod == arg) return Qtrue;

    if (RB_TYPE_P(arg, T_CLASS) && RB_TYPE_P(mod, T_CLASS)) {
        // comparison between classes
        size_t mod_depth = RCLASS_SUPERCLASS_DEPTH(mod);
        size_t arg_depth = RCLASS_SUPERCLASS_DEPTH(arg);
        if (arg_depth < mod_depth) {
            // check if mod < arg
            return RCLASS_SUPERCLASSES(mod)[arg_depth] == arg ?
                Qtrue :
                Qnil;
        }
        else if (arg_depth > mod_depth) {
            // check if mod > arg
            return RCLASS_SUPERCLASSES(arg)[mod_depth] == mod ?
                Qfalse :
                Qnil;
        }
        else {
            // Depths match, and we know they aren't equal: no relation
            return Qnil;
        }
    }
    else {
        if (!CLASS_OR_MODULE_P(arg) && !RB_TYPE_P(arg, T_ICLASS)) {
            rb_raise(rb_eTypeError, "compared with non class/module");
        }
        if (class_search_ancestor(mod, RCLASS_ORIGIN(arg))) {
            return Qtrue;
        }
        /* not mod < arg; check if mod > arg */
        if (class_search_ancestor(arg, mod)) {
            return Qfalse;
        }
        return Qnil;
    }
}

Compares self and other with respect to ancestry and inclusion.

Returns nil if there is no such relationship between the two:

Array <= Hash       # => nil

Otherwise, returns true if other is an ancestor of self, or if self includes other, or if the two are the same:

File  <= IO         # => true  # IO is an ancestor of File.
Array <= Enumerable # => true  # Array includes Enumerable.
Array <= Array      # => true

Otherwise, returns false:

IO         <= File  # => false
Enumerable <= Array # => false

static VALUE
rb_mod_cmp(VALUE mod, VALUE arg)
{
    VALUE cmp;

    if (mod == arg) return INT2FIX(0);
    if (!CLASS_OR_MODULE_P(arg)) {
        return Qnil;
    }

    cmp = rb_class_inherited_p(mod, arg);
    if (NIL_P(cmp)) return Qnil;
    if (cmp) {
        return INT2FIX(-1);
    }
    return INT2FIX(1);
}

Compares self and other.

Returns:

• -1, if self includes other, if or self is a subclass of other.

• 0, if self and other are the same.

• 1, if other includes self, or if other is a subclass of self.

• nil, if none of the above is true.

Examples:

         # Class Array includes module Enumerable.
         Array <=> Enumerable # => -1
    Enumerable <=> Enumerable # =>  0
    Enumerable <=> Array      # =>  1
# Class File is a subclass of class IO.
          File <=> IO         # => -1
          File <=> File       # =>  0
            IO <=> File       # =>  1
# Class File has no relationship to class String.
          File <=> String     # => nil

VALUE
rb_obj_equal(VALUE obj1, VALUE obj2)
{
    return RBOOL(obj1 == obj2);
}

Returns whether self and other are the same object:

object = Object.new
object == object     # => true
object == Object.new # => false

Here in class Object, ==, equal?, and eql? are the same method. A subclass may override == to provide class-specific meaning.

Unlike ==, the equal? method should never be overridden by subclasses as it is used to determine object identity (that is, a.equal?(b) if and only if a is the same object as b):

obj = "a"
other = obj.dup

obj == other      #=> true
obj.equal? other  #=> false
obj.equal? obj    #=> true

The eql? method returns true if obj and other refer to the same hash key. This is used by Hash to test members for equality. For any pair of objects where eql? returns true, the hash value of both objects must be equal. So any subclass that overrides eql? should also override hash appropriately.

For objects of class Object, eql? is synonymous with ==. Subclasses normally continue this tradition by aliasing eql? to their overridden == method, but there are exceptions. Numeric types, for example, perform type conversion across ==, but not across eql?, so:

1 == 1.0     #=> true
1.eql? 1.0   #=> false

static VALUE
rb_mod_eqq(VALUE mod, VALUE arg)
{
    return rb_obj_is_kind_of(arg, mod);
}

Returns whether other is an instance of self, or is an instance of a subclass of self.

Of limited use for modules, but can be used in case statements to classify objects by class.

static VALUE
rb_mod_gt(VALUE mod, VALUE arg)
{
    if (mod == arg) return Qfalse;
    return rb_mod_ge(mod, arg);
}

Returns true if self is an ancestor of other (self is a superclass of other or self is included in other):

Numeric > Float    # => true
Enumerable > Array # => true

Returns false if self is a descendant of other (self is a subclass of other or self includes other) or if self is the same as other:

Float > Numeric    # => false
Array > Enumerable # => false
Float > Float      # => false

Returns nil if there is no relationship between the two:

Float > Hash        # => nil
Enumerable > String # => nil

static VALUE
rb_mod_ge(VALUE mod, VALUE arg)
{
    if (!CLASS_OR_MODULE_P(arg)) {
        rb_raise(rb_eTypeError, "compared with non class/module");
    }

    return rb_class_inherited_p(arg, mod);
}

Compares self and other with respect to ancestry and inclusion.

Returns true if self is an ancestor of other (self is a superclass of other or self is included in other) or if self is the same as other:

Numeric >= Float    # => true
Enumerable >= Array # => true
Float >= Float      # => true

Returns false if self is a descendant of other (self is a subclass of other or self includes other):

Float >= Numeric    # => false
Array >= Enumerable # => false

Returns nil if there is no relationship between the two:

Float >= Hash        # => nil
Enumerable >= String # => nil

static VALUE
rb_mod_alias_method(VALUE mod, VALUE newname, VALUE oldname)
{
    ID oldid = rb_check_id(&oldname);
    if (!oldid) {
        rb_print_undef_str(mod, oldname);
    }
    VALUE id = rb_to_id(newname);
    rb_alias(mod, id, oldid);
    return ID2SYM(id);
}

Makes new_name a new copy of the method old_name. This can be used to retain access to methods that are overridden.

class Greeter
  def hello
    "hello"
  end
  alias_method :orig_hello, :hello #=> :orig_hello
  def hello
    "#{orig_hello}, world"
  end
end
Greeter.new.hello #=> "hello, world"

In a module, old_name must be a method of the module or its ancestors. Aliasing a method found only through the fallback to Object is deprecated, and will raise a NameError in Ruby 4.3.

VALUE
rb_mod_ancestors(VALUE mod)
{
    VALUE p, ary = rb_ary_new();
    VALUE refined_class = Qnil;
    if (BUILTIN_TYPE(mod) == T_MODULE && FL_TEST(mod, RMODULE_IS_REFINEMENT)) {
        refined_class = rb_refinement_module_get_refined_class(mod);
    }

    for (p = mod; p; p = RCLASS_SUPER(p)) {
        if (p == refined_class) break;
        if (p != RCLASS_ORIGIN(p)) continue;
        if (BUILTIN_TYPE(p) == T_ICLASS) {
            rb_ary_push(ary, METACLASS_OF(p));
        }
        else {
            rb_ary_push(ary, p);
        }
    }
    return ary;
}

Returns an array of the modules that are ancestors of self and that self includes or prepends, including self:

module MyModule
  include Math
  include Comparable
  prepend Enumerable
end
MyModule.ancestors    # => [Enumerable, MyModule, Comparable, Math]

class MyClass; end
MyClass.ancestors     # => [MyClass, Object, JSON::GeneratorMethods, PP::ObjectMixin, Kernel, BasicObject]

Object.ancestors      # => [Object, JSON::GeneratorMethods, PP::ObjectMixin, Kernel, BasicObject]
BasicObject.ancestors # => [BasicObject]

VALUE
rb_mod_attr(int argc, VALUE *argv, VALUE klass)
{
    if (argc == 2 && (argv[1] == Qtrue || argv[1] == Qfalse)) {
        ID id = id_for_attr(klass, argv[0]);
        VALUE names = rb_ary_new();

        rb_category_warning(RB_WARN_CATEGORY_DEPRECATED, "optional boolean argument is obsoleted");
        rb_attr(klass, id, 1, RTEST(argv[1]), TRUE);
        rb_ary_push(names, ID2SYM(id));
        if (argv[1] == Qtrue) rb_ary_push(names, ID2SYM(rb_id_attrset(id)));
        return names;
    }
    return rb_mod_attr_reader(argc, argv, klass);
}

The first form is equivalent to attr_reader. The second form is equivalent to attr_accessor(name) but deprecated. The last form is equivalent to attr_reader(name) but deprecated. Returns an array of defined method names as symbols.

static VALUE
rb_mod_attr_accessor(int argc, VALUE *argv, VALUE klass)
{
    int i;
    VALUE names = rb_ary_new2(argc * 2);

    for (i=0; i<argc; i++) {
        ID id = id_for_attr(klass, argv[i]);

        rb_attr(klass, id, TRUE, TRUE, TRUE);
        rb_ary_push(names, ID2SYM(id));
        rb_ary_push(names, ID2SYM(rb_id_attrset(id)));
    }
    return names;
}

Defines a named attribute for this module, where the name is symbol.id2name, creating an instance variable (@name) and a corresponding access method to read it. Also creates a method called name= to set the attribute. String arguments are converted to symbols. Returns an array of defined method names as symbols.

module Mod
  attr_accessor(:one, :two) #=> [:one, :one=, :two, :two=]
end
Mod.instance_methods.sort   #=> [:one, :one=, :two, :two=]

static VALUE
rb_mod_attr_reader(int argc, VALUE *argv, VALUE klass)
{
    int i;
    VALUE names = rb_ary_new2(argc);

    for (i=0; i<argc; i++) {
        ID id = id_for_attr(klass, argv[i]);
        rb_attr(klass, id, TRUE, FALSE, TRUE);
        rb_ary_push(names, ID2SYM(id));
    }
    return names;
}

Creates instance variables and corresponding methods that return the value of each instance variable. Equivalent to calling “attr:name” on each name in turn. String arguments are converted to symbols. Returns an array of defined method names as symbols.

static VALUE
rb_mod_attr_writer(int argc, VALUE *argv, VALUE klass)
{
    int i;
    VALUE names = rb_ary_new2(argc);

    for (i=0; i<argc; i++) {
        ID id = id_for_attr(klass, argv[i]);
        rb_attr(klass, id, FALSE, TRUE, TRUE);
        rb_ary_push(names, ID2SYM(rb_id_attrset(id)));
    }
    return names;
}

Creates an accessor method to allow assignment to the attribute symbol.id2name. String arguments are converted to symbols. Returns an array of defined method names as symbols.

static VALUE
rb_mod_autoload(VALUE mod, VALUE sym, VALUE file)
{
    ID id = rb_to_id(sym);

    FilePathValue(file);
    rb_autoload_str(mod, id, file);
    return Qnil;
}

Registers filename to be loaded (using Kernel::require) the first time that const (which may be a String or a symbol) is accessed in the namespace of mod.

module A
end
A.autoload(:B, "b")
A::B.doit            # autoloads "b"

If const in mod is defined as autoload, the file name to be loaded is replaced with filename. If const is defined but not as autoload, does nothing.

Files that are currently being loaded must not be registered for autoload.

static VALUE
rb_mod_autoload_p(int argc, VALUE *argv, VALUE mod)
{
    int recur = (rb_check_arity(argc, 1, 2) == 1) ? TRUE : RTEST(argv[1]);
    VALUE sym = argv[0];

    ID id = rb_check_id(&sym);
    if (!id) {
        return Qnil;
    }
    return rb_autoload_at_p(mod, id, recur);
}

Returns filename to be loaded if name is registered as autoload in the namespace of mod or one of its ancestors.

module A
end
A.autoload(:B, "b")
A.autoload?(:B)            #=> "b"

If inherit is false, the lookup only checks the autoloads in the receiver:

class A
  autoload :CONST, "const.rb"
end

class B < A
end

B.autoload?(:CONST)          #=> "const.rb", found in A (ancestor)
B.autoload?(:CONST, false)   #=> nil, not found in B itself

static VALUE
rb_mod_autoload_relative(VALUE mod, VALUE sym, VALUE file)
{
    ID id = rb_to_id(sym);
    VALUE base, absolute_path;

    FilePathValue(file);

    base = rb_current_realfilepath();
    if (NIL_P(base)) {
        rb_loaderror("cannot infer basepath (autoload_relative called without file context)");
    }
    base = rb_file_dirname(base);
    absolute_path = rb_file_absolute_path(file, base);

    rb_autoload_str(mod, id, absolute_path);
    return Qnil;
}

Registers filename to be loaded (using Kernel::require) the first time that const (which may be a String or a symbol) is accessed in the namespace of mod. The filename is interpreted as relative to the directory of the file where autoload_relative is called.

module A
end
A.autoload_relative(:B, "b.rb")

If const in mod is defined as autoload, the file name to be loaded is replaced with filename. If const is defined but not as autoload, does nothing.

The relative path is converted to an absolute path, which is what will be returned by Module#autoload? for the constant.

Raises LoadError if called without file context (e.g., from eval).

Evaluates the string or block in the context of self. Returns the result of the last expression.

When string is given, evaluates the given string in the context of self:

class Foo; end

Foo.module_eval("def greeting = puts 'hello'")

Foo.new.greeting # => "hello"

If the optional filename is given, it will be used as the filename of the evaluation (for __FILE__ and errors). Otherwise, it will default to (eval at __FILE__:__LINE__) where __FILE__ and __LINE__ are the filename and line number of the caller, respectively:

class Foo; end

Foo.module_eval("puts __FILE__") # => "(eval at ../test.rb:3)"
Foo.module_eval("puts __FILE__", "foobar.rb") # => "foobar.rb"

If the optional lineno is given, it will be used as the line number of the evaluation (for __LINE__ and errors). Otherwise, it will default to 1:

class Foo; end

Foo.module_eval("puts __LINE__") # => 1
Foo.module_eval("puts __LINE__", nil, 10) # => 10

When a block is given, evaluates the block in the context of self:

class Foo; end

Foo.module_eval do
  def greeting = puts "hello"
end

Foo.new.greeting

However, constant and class variable lookup differs between string and block. When string is given, constant and class variables are looked up in the context of self. When a block is given, the context of the lookup is not changed:

class Foo
  GREETING = "hello"
end

Foo.module_eval("puts GREETING") # => "hello"

Foo.module_eval { puts GREETING } # => NameError: uninitialized constant GREETING

Evaluates the given block in the context of the class/module. The method defined in the block will belong to the receiver. Any arguments passed to the method will be passed to the block. This can be used if the block needs to access instance variables.

class Thing
end
Thing.class_exec{
  def hello() "Hello there!" end
}
puts Thing.new.hello()

produces:

Hello there!

static VALUE
rb_mod_cvar_defined(VALUE obj, VALUE iv)
{
    ID id = id_for_var(obj, iv, class);

    if (!id) {
        return Qfalse;
    }
    return rb_cvar_defined(obj, id);
}

Returns true if the given class variable is defined in obj. String arguments are converted to symbols.

class Fred
  @@foo = 99
end
Fred.class_variable_defined?(:@@foo)    #=> true
Fred.class_variable_defined?(:@@bar)    #=> false

static VALUE
rb_mod_cvar_get(VALUE obj, VALUE iv)
{
    ID id = id_for_var(obj, iv, class);

    if (!id) {
        rb_name_err_raise("uninitialized class variable %1$s in %2$s",
                          obj, iv);
    }
    return rb_cvar_get(obj, id);
}

Returns the value of the given class variable (or throws a NameError exception). The @@ part of the variable name should be included for regular class variables. String arguments are converted to symbols.

class Fred
  @@foo = 99
end
Fred.class_variable_get(:@@foo)     #=> 99

static VALUE
rb_mod_cvar_set(VALUE obj, VALUE iv, VALUE val)
{
    ID id = id_for_var(obj, iv, class);
    if (!id) id = rb_intern_str(iv);
    rb_cvar_set(obj, id, val);
    return val;
}

Sets the class variable named by symbol to the given object. If the class variable name is passed as a string, that string is converted to a symbol.

class Fred
  @@foo = 99
  def foo
    @@foo
  end
end
Fred.class_variable_set(:@@foo, 101)     #=> 101
Fred.new.foo                             #=> 101

VALUE
rb_mod_class_variables(int argc, const VALUE *argv, VALUE mod)
{
    bool inherit = true;
    st_table *tbl;

    if (rb_check_arity(argc, 0, 1)) inherit = RTEST(argv[0]);
    if (inherit) {
        tbl = mod_cvar_of(mod, 0);
    }
    else {
        tbl = mod_cvar_at(mod, 0);
    }
    return cvar_list(tbl);
}

Returns an array of the names of class variables in mod. This includes the names of class variables in any included modules, unless the inherit parameter is set to false.

class One
  @@var1 = 1
end
class Two < One
  @@var2 = 2
end
One.class_variables          #=> [:@@var1]
Two.class_variables          #=> [:@@var2, :@@var1]
Two.class_variables(false)   #=> [:@@var2]

static VALUE
rb_mod_const_defined(int argc, VALUE *argv, VALUE mod)
{
    VALUE name, recur;
    rb_encoding *enc;
    const char *pbeg, *p, *path, *pend;
    ID id;

    rb_check_arity(argc, 1, 2);
    name = argv[0];
    recur = (argc == 1) ? Qtrue : argv[1];

    if (SYMBOL_P(name)) {
        if (!rb_is_const_sym(name)) goto wrong_name;
        id = rb_check_id(&name);
        if (!id) return Qfalse;
        return RTEST(recur) ? rb_const_defined(mod, id) : rb_const_defined_at(mod, id);
    }

    path = StringValuePtr(name);
    enc = rb_enc_get(name);

    if (!rb_enc_asciicompat(enc)) {
        rb_raise(rb_eArgError, "invalid class path encoding (non ASCII)");
    }

    pbeg = p = path;
    pend = path + RSTRING_LEN(name);

    if (p >= pend || !*p) {
        goto wrong_name;
    }

    if (p + 2 < pend && p[0] == ':' && p[1] == ':') {
        mod = rb_cObject;
        p += 2;
        pbeg = p;
    }

    while (p < pend) {
        VALUE part;
        rb_len_t len, beglen;

        while (p < pend && *p != ':') p++;

        if (pbeg == p) goto wrong_name;

        id = rb_check_id_cstr(pbeg, len = p-pbeg, enc);
        beglen = pbeg-path;

        if (p < pend && p[0] == ':') {
            if (p + 2 >= pend || p[1] != ':') goto wrong_name;
            p += 2;
            pbeg = p;
        }

        if (!id) {
            part = rb_str_subseq(name, beglen, len);
            OBJ_FREEZE(part);
            if (!rb_is_const_name(part)) {
                name = part;
                goto wrong_name;
            }
            else {
                return Qfalse;
            }
        }
        if (!rb_is_const_id(id)) {
            name = ID2SYM(id);
            goto wrong_name;
        }

#if 0
        mod = rb_const_search(mod, id, beglen > 0 || !RTEST(recur), RTEST(recur), FALSE);
        if (UNDEF_P(mod)) return Qfalse;
#else
        if (!RTEST(recur)) {
            if (!rb_const_defined_at(mod, id))
                return Qfalse;
            if (p == pend) return Qtrue;
            mod = rb_const_get_at(mod, id);
        }
        else if (beglen == 0) {
            if (!rb_const_defined(mod, id))
                return Qfalse;
            if (p == pend) return Qtrue;
            mod = rb_const_get(mod, id);
        }
        else {
            if (!rb_const_defined_from(mod, id))
                return Qfalse;
            if (p == pend) return Qtrue;
            mod = rb_const_get_from(mod, id);
        }
#endif

        if (p < pend && !RB_TYPE_P(mod, T_MODULE) && !RB_TYPE_P(mod, T_CLASS)) {
            rb_raise(rb_eTypeError, "%"PRIsVALUE" does not refer to class/module",
                     QUOTE(name));
        }
    }

    return Qtrue;

  wrong_name:
    rb_name_err_raise(wrong_constant_name, mod, name);
    UNREACHABLE_RETURN(Qundef);
}

Says whether mod or its ancestors have a constant with the given name:

Float.const_defined?(:EPSILON)      #=> true, found in Float itself
Float.const_defined?("String")      #=> true, found in Object (ancestor)
BasicObject.const_defined?(:Hash)   #=> false

If mod is a Module, additionally Object and its ancestors are checked:

Math.const_defined?(:String)   #=> true, found in Object

In each of the checked classes or modules, if the constant is not present but there is an autoload for it, true is returned directly without autoloading:

module Admin
  autoload :User, 'admin/user'
end
Admin.const_defined?(:User)   #=> true

If the constant is not found the callback const_missing is not called and the method returns false.

If inherit is false, the lookup only checks the constants in the receiver:

IO.const_defined?(:SYNC)          #=> true, found in File::Constants (ancestor)
IO.const_defined?(:SYNC, false)   #=> false, not found in IO itself

In this case, the same logic for autoloading applies.

If the argument is not a valid constant name a NameError is raised with the message “wrong constant name name”:

Hash.const_defined? 'foobar'   #=> NameError: wrong constant name foobar

static VALUE
rb_mod_const_get(int argc, VALUE *argv, VALUE mod)
{
    VALUE name, recur;
    rb_encoding *enc;
    const char *pbeg, *p, *path, *pend;
    ID id;

    rb_check_arity(argc, 1, 2);
    name = argv[0];
    recur = (argc == 1) ? Qtrue : argv[1];

    if (SYMBOL_P(name)) {
        if (!rb_is_const_sym(name)) goto wrong_name;
        id = rb_check_id(&name);
        if (!id) return rb_const_missing(mod, name);
        return RTEST(recur) ? rb_const_get(mod, id) : rb_const_get_at(mod, id);
    }

    path = StringValuePtr(name);
    enc = rb_enc_get(name);

    if (!rb_enc_asciicompat(enc)) {
        rb_raise(rb_eArgError, "invalid class path encoding (non ASCII)");
    }

    pbeg = p = path;
    pend = path + RSTRING_LEN(name);

    if (p >= pend || !*p) {
        goto wrong_name;
    }

    if (p + 2 < pend && p[0] == ':' && p[1] == ':') {
        mod = rb_cObject;
        p += 2;
        pbeg = p;
    }

    while (p < pend) {
        VALUE part;
        rb_len_t len, beglen;

        while (p < pend && *p != ':') p++;

        if (pbeg == p) goto wrong_name;

        id = rb_check_id_cstr(pbeg, len = p-pbeg, enc);
        beglen = pbeg-path;

        if (p < pend && p[0] == ':') {
            if (p + 2 >= pend || p[1] != ':') goto wrong_name;
            p += 2;
            pbeg = p;
        }

        if (!RB_TYPE_P(mod, T_MODULE) && !RB_TYPE_P(mod, T_CLASS)) {
            rb_raise(rb_eTypeError, "%"PRIsVALUE" does not refer to class/module",
                     QUOTE(name));
        }

        if (!id) {
            part = rb_str_subseq(name, beglen, len);
            OBJ_FREEZE(part);
            if (!rb_is_const_name(part)) {
                name = part;
                goto wrong_name;
            }
            else if (!rb_method_basic_definition_p(CLASS_OF(mod), id_const_missing)) {
                part = rb_str_intern(part);
                mod = rb_const_missing(mod, part);
                continue;
            }
            else {
                rb_mod_const_missing(mod, part);
            }
        }
        if (!rb_is_const_id(id)) {
            name = ID2SYM(id);
            goto wrong_name;
        }
#if 0
        mod = rb_const_get_0(mod, id, beglen > 0 || !RTEST(recur), RTEST(recur), FALSE);
#else
        if (!RTEST(recur)) {
            mod = rb_const_get_at(mod, id);
        }
        else if (beglen == 0) {
            mod = rb_const_get(mod, id);
        }
        else {
            mod = rb_const_get_from(mod, id);
        }
#endif
    }

    return mod;

  wrong_name:
    rb_name_err_raise(wrong_constant_name, mod, name);
    UNREACHABLE_RETURN(Qundef);
}

Checks for a constant with the given name in mod. If inherit is set, the lookup will also search the ancestors (and Object if mod is a Module).

The value of the constant is returned if a definition is found, otherwise a NameError is raised.

Math.const_get(:PI)   #=> 3.141592653589793

This method will recursively look up constant names if a namespaced class name is provided. For example:

module Foo; class Bar; end end
Object.const_get 'Foo::Bar'

The inherit flag is respected on each lookup. For example:

module Foo
  class Bar
    VAL = 10
  end

  class Baz < Bar; end
end

Object.const_get 'Foo::Baz::VAL'         # => 10
Object.const_get 'Foo::Baz::VAL', false  # => NameError

If the argument is not a valid constant name a NameError will be raised with a warning “wrong constant name”.

Object.const_get 'foobar' #=> NameError: wrong constant name foobar

VALUE
rb_mod_const_missing(VALUE klass, VALUE name)
{
    rb_execution_context_t *ec = GET_EC();
    VALUE ref = ec->private_const_reference;
    rb_vm_pop_cfunc_frame();
    if (ref) {
        ec->private_const_reference = 0;
        rb_name_err_raise("private constant %2$s::%1$s referenced", ref, name);
    }
    uninitialized_constant(klass, name);

    UNREACHABLE_RETURN(Qnil);
}

Invoked when a reference is made to an undefined constant in mod. It is passed a symbol for the undefined constant, and returns a value to be used for that constant. For example, consider:

def Foo.const_missing(name)
  name # return the constant name as Symbol
end

Foo::UNDEFINED_CONST    #=> :UNDEFINED_CONST: symbol returned

As the example above shows, const_missing is not required to create the missing constant in mod, though that is often a side-effect. The caller gets its return value when triggered. If the constant is also defined, further lookups won’t hit const_missing and will return the value stored in the constant as usual. Otherwise, const_missing will be invoked again.

In the next example, when a reference is made to an undefined constant, const_missing attempts to load a file whose path is the lowercase version of the constant name (thus class Fred is assumed to be in file fred.rb). If defined as a side-effect of loading the file, the method returns the value stored in the constant. This implements an autoload feature similar to Kernel#autoload and Module#autoload, though it differs in important ways.

def Object.const_missing(name)
  @looked_for ||= {}
  str_name = name.to_s
  raise "Constant not found: #{name}" if @looked_for[str_name]
  @looked_for[str_name] = 1
  file = str_name.downcase
  require file
  const_get(name, false)
end

static VALUE
rb_mod_const_set(VALUE mod, VALUE name, VALUE value)
{
    ID id = id_for_var(mod, name, const);
    if (!id) id = rb_intern_str(name);
    rb_const_set(mod, id, value);

    return value;
}

Sets the named constant to the given object, returning that object. Creates a new constant if no constant with the given name previously existed.

Math.const_set("HIGH_SCHOOL_PI", 22.0/7.0)   #=> 3.142857142857143
Math::HIGH_SCHOOL_PI - Math::PI              #=> 0.0012644892673496777

If sym or str is not a valid constant name a NameError will be raised with a warning “wrong constant name”.

Object.const_set('foobar', 42) #=> NameError: wrong constant name foobar

static VALUE
rb_mod_const_source_location(int argc, VALUE *argv, VALUE mod)
{
    VALUE name, recur, loc = Qnil;
    rb_encoding *enc;
    const char *pbeg, *p, *path, *pend;
    ID id;

    rb_check_arity(argc, 1, 2);
    name = argv[0];
    recur = (argc == 1) ? Qtrue : argv[1];

    if (SYMBOL_P(name)) {
        if (!rb_is_const_sym(name)) goto wrong_name;
        id = rb_check_id(&name);
        if (!id) return Qnil;
        return RTEST(recur) ? rb_const_source_location(mod, id) : rb_const_source_location_at(mod, id);
    }

    path = StringValuePtr(name);
    enc = rb_enc_get(name);

    if (!rb_enc_asciicompat(enc)) {
        rb_raise(rb_eArgError, "invalid class path encoding (non ASCII)");
    }

    pbeg = p = path;
    pend = path + RSTRING_LEN(name);

    if (p >= pend || !*p) {
        goto wrong_name;
    }

    if (p + 2 < pend && p[0] == ':' && p[1] == ':') {
        mod = rb_cObject;
        p += 2;
        pbeg = p;
    }

    while (p < pend) {
        VALUE part;
        rb_len_t len, beglen;

        while (p < pend && *p != ':') p++;

        if (pbeg == p) goto wrong_name;

        id = rb_check_id_cstr(pbeg, len = p-pbeg, enc);
        beglen = pbeg-path;

        if (p < pend && p[0] == ':') {
            if (p + 2 >= pend || p[1] != ':') goto wrong_name;
            p += 2;
            pbeg = p;
        }

        if (!id) {
            part = rb_str_subseq(name, beglen, len);
            OBJ_FREEZE(part);
            if (!rb_is_const_name(part)) {
                name = part;
                goto wrong_name;
            }
            else {
                return Qnil;
            }
        }
        if (!rb_is_const_id(id)) {
            name = ID2SYM(id);
            goto wrong_name;
        }
        if (p < pend) {
            if (RTEST(recur)) {
                mod = rb_const_get(mod, id);
            }
            else {
                mod = rb_const_get_at(mod, id);
            }
            if (!RB_TYPE_P(mod, T_MODULE) && !RB_TYPE_P(mod, T_CLASS)) {
                rb_raise(rb_eTypeError, "%"PRIsVALUE" does not refer to class/module",
                         QUOTE(name));
            }
        }
        else {
            if (RTEST(recur)) {
                loc = rb_const_source_location(mod, id);
            }
            else {
                loc = rb_const_source_location_at(mod, id);
            }
            break;
        }
        recur = Qfalse;
    }

    return loc;

  wrong_name:
    rb_name_err_raise(wrong_constant_name, mod, name);
    UNREACHABLE_RETURN(Qundef);
}

Returns the Ruby source filename and line number containing the definition of the constant specified. If the named constant is not found, nil is returned. If the constant is found, but its source location can not be extracted (constant is defined in C code), empty array is returned.

inherit specifies whether to lookup in mod.ancestors (true by default).

# test.rb:
class A         # line 1
  C1 = 1
  C2 = 2
end

module M        # line 6
  C3 = 3
end

class B < A     # line 10
  include M
  C4 = 4
end

class A # continuation of A definition
  C2 = 8 # constant redefinition; warned yet allowed
end

p B.const_source_location('C4')           # => ["test.rb", 12]
p B.const_source_location('C3')           # => ["test.rb", 7]
p B.const_source_location('C1')           # => ["test.rb", 2]

p B.const_source_location('C3', false)    # => nil  -- don't lookup in ancestors

p A.const_source_location('C2')           # => ["test.rb", 16] -- actual (last) definition place

p Object.const_source_location('B')       # => ["test.rb", 10] -- top-level constant could be looked through Object
p Object.const_source_location('A')       # => ["test.rb", 1] -- class reopening is NOT considered new definition

p B.const_source_location('A')            # => ["test.rb", 1]  -- because Object is in ancestors
p M.const_source_location('A')            # => ["test.rb", 1]  -- Object is not ancestor, but additionally checked for modules

p Object.const_source_location('A::C1')   # => ["test.rb", 2]  -- nesting is supported
p Object.const_source_location('String')  # => []  -- constant is defined in C code

VALUE
rb_mod_constants(int argc, const VALUE *argv, VALUE mod)
{
    bool inherit = true;

    if (rb_check_arity(argc, 0, 1)) inherit = RTEST(argv[0]);

    if (inherit) {
        return rb_const_list(rb_mod_const_of(mod, 0));
    }
    else {
        return rb_local_constants(mod);
    }
}

Returns an array of the names of the constants accessible in mod. This includes the names of constants in any included modules (example at start of section), unless the inherit parameter is set to false.

The implementation makes no guarantees about the order in which the constants are yielded.

IO.constants.include?(:SYNC)        #=> true
IO.constants(false).include?(:SYNC) #=> false

Also see Module#const_defined?.

static VALUE
rb_mod_define_method(int argc, VALUE *argv, VALUE mod)
{
    const rb_cref_t *cref = rb_vm_cref_in_context(mod, mod);
    const rb_scope_visibility_t default_scope_visi = {METHOD_VISI_PUBLIC, FALSE};
    const rb_scope_visibility_t *scope_visi = &default_scope_visi;

    if (cref) {
        scope_visi = CREF_SCOPE_VISI(cref);
    }

    return rb_mod_define_method_with_visibility(argc, argv, mod, scope_visi);
}

Defines an instance method in the receiver. The method parameter can be a Proc, a Method or an UnboundMethod object. If a block is specified, it is used as the method body. If a block or the method parameter has parameters, they’re used as method parameters. This block is evaluated using instance_eval.

class A
  def fred
    puts "In Fred"
  end
  def create_method(name, &block)
    self.class.define_method(name, &block)
  end
  define_method(:wilma) { puts "Charge it!" }
  define_method(:flint) {|name| puts "I'm #{name}!"}
end
class B < A
  define_method(:barney, instance_method(:fred))
end
a = B.new
a.barney
a.wilma
a.flint('Dino')
a.create_method(:betty) { p self }
a.betty

produces:

In Fred
Charge it!
I'm Dino!
#<B:0x401b39e8>

VALUE
rb_mod_deprecate_constant(int argc, const VALUE *argv, VALUE obj)
{
    set_const_visibility(obj, argc, argv, CONST_DEPRECATED, CONST_DEPRECATED);
    return obj;
}

Makes a list of existing constants deprecated. Attempt to refer to them will produce a warning.

module HTTP
  NotFound = Exception.new
  NOT_FOUND = NotFound # previous version of the library used this name

  deprecate_constant :NOT_FOUND
end

HTTP::NOT_FOUND
# warning: constant HTTP::NOT_FOUND is deprecated

VALUE
rb_mod_descendants(VALUE mod)
{
    struct descendants_traverse_data data = { Qfalse, 0, -1, NULL };

    // estimate the count of descendants
    data.visited = st_init_numtable();
    st_insert(data.visited, (st_data_t)mod, 1); // exclude the receiver
    rb_class_foreach_subclass(mod, module_descendants_recursive, (VALUE)&data);
    st_free_table(data.visited);

    // the following allocation may cause GC which may change the number of descendants
    data.buffer = rb_ary_new_capa(data.count);
    data.maxcount = data.count;
    data.count = 0;
    // pre-sized so that st_insert() does not cause GC during the enumeration
    data.visited = st_init_numtable_with_size(data.maxcount + 1);
    st_insert(data.visited, (st_data_t)mod, 1); // exclude the receiver

    size_t gc_count = rb_gc_count();

    rb_class_foreach_subclass(mod, module_descendants_recursive, (VALUE)&data);

    if (gc_count != rb_gc_count()) {
        rb_bug("GC must not occur during the subclass iteration of Module#descendants");
    }
    st_free_table(data.visited);

    return data.buffer;
}

Returns an array of classes and modules that have self as an ancestor. Singleton classes and refinements are not included. The order of the returned array is not defined.

module A; end
module B; include A; end
class C; include B; end
class D < C; end

A.descendants    #=> [B, C, D]
B.descendants    #=> [C, D]
C.descendants    #=> [D]

Note that self does not hold references to its descendants; Thus even though all references to a module are dropped, the module may be reported as a descendant, depending on garbage collection.

static VALUE
rb_mod_freeze(VALUE mod)
{
    // a permanent modification; already frozen changes no state, so stays a no-op
    if (!OBJ_FROZEN(mod)) {
        rb_class_owner_check(mod);
    }
    rb_class_name(mod);
    return rb_obj_freeze(mod);
}

Prevents further modifications to mod.

This method returns self.

static VALUE
rb_mod_include(int argc, VALUE *argv, VALUE module)
{
    int i;
    ID id_append_features, id_included;

    CONST_ID(id_append_features, "append_features");
    CONST_ID(id_included, "included");

    if (BUILTIN_TYPE(module) == T_MODULE && FL_TEST(module, RMODULE_IS_REFINEMENT)) {
        rb_raise(rb_eTypeError, "Refinement#include has been removed");
    }

    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    for (i = 0; i < argc; i++) {
        Check_Type(argv[i], T_MODULE);
        if (FL_TEST(argv[i], RMODULE_IS_REFINEMENT)) {
            rb_raise(rb_eTypeError, "Cannot include refinement");
        }
    }
    while (argc--) {
        rb_funcallv_uncached(argv[argc], id_append_features, 1, &module);
        rb_funcallv_uncached(argv[argc], id_included, 1, &module);
    }
    return module;
}

Invokes Module.append_features on each parameter in reverse order.

VALUE
rb_mod_include_p(VALUE mod, VALUE mod2)
{
    VALUE p;

    Check_Type(mod2, T_MODULE);
    for (p = RCLASS_SUPER(mod); p; p = RCLASS_SUPER(p)) {
        if (BUILTIN_TYPE(p) == T_ICLASS && !RICLASS_IS_ORIGIN_P(p)) {
            if (METACLASS_OF(p) == mod2) return Qtrue;
        }
    }
    return Qfalse;
}

Returns true if module is included or prepended in mod or one of mod‘s ancestors.

module A
end
class B
  include A
end
class C < B
end
B.include?(A)   #=> true
C.include?(A)   #=> true
A.include?(A)   #=> false

VALUE
rb_mod_included_modules(VALUE mod)
{
    VALUE ary = rb_ary_new();
    VALUE p;
    VALUE origin = RCLASS_ORIGIN(mod);

    for (p = RCLASS_SUPER(mod); p; p = RCLASS_SUPER(p)) {
        if (p != origin && RCLASS_ORIGIN(p) == p && BUILTIN_TYPE(p) == T_ICLASS) {
            VALUE m = METACLASS_OF(p);
            if (RB_TYPE_P(m, T_MODULE))
                rb_ary_push(ary, m);
        }
    }
    return ary;
}

Returns the list of modules included or prepended in mod or one of mod‘s ancestors.

module Sub
end

module Mixin
  prepend Sub
end

module Outer
  include Mixin
end

Mixin.included_modules   #=> [Sub]
Outer.included_modules   #=> [Sub, Mixin]

static VALUE
rb_mod_instance_method(VALUE mod, VALUE vid)
{
    ID id = rb_check_id(&vid);
    if (!id) {
        rb_method_name_error(mod, vid);
    }
    return mnew_unbound(mod, id, rb_cUnboundMethod, FALSE);
}

Returns an UnboundMethod representing the given instance method in mod. See UnboundMethod about how to utilize it

class Person
  def initialize(name)
    @name = name
  end

  def hi
    puts "Hi, I'm #{@name}!"
  end
end

 dave = Person.new('Dave')
 thomas = Person.new('Thomas')

 hi = Person.instance_method(:hi)
 hi.bind_call(dave)
 hi.bind_call(thomas)

produces:

Hi, I'm Dave!
Hi, I'm Thomas!

VALUE
rb_class_instance_methods(int argc, const VALUE *argv, VALUE mod)
{
    return class_instance_method_list(argc, argv, mod, 0, ins_methods_i);
}

Returns an array containing the names of the public and protected instance methods in the receiver. For a module, these are the public and protected methods; for a class, they are the instance (not singleton) methods. If the optional parameter is false, the methods of any ancestors are not included.

module A
  def method1()  end
end
class B
  include A
  def method2()  end
end
class C < B
  def method3()  end
end

A.instance_methods(false)                   #=> [:method1]
B.instance_methods(false)                   #=> [:method2]
B.instance_methods(true).include?(:method1) #=> true
C.instance_methods(false)                   #=> [:method3]
C.instance_methods.include?(:method2)       #=> true

Note that method visibility changes in the current class, as well as aliases, are considered as methods of the current class by this method:

class C < B
  alias method4 method2
  protected :method2
end
C.instance_methods(false).sort               #=> [:method2, :method3, :method4]

static VALUE
rb_mod_method_defined(int argc, VALUE *argv, VALUE mod)
{
    VALUE mid, include_super, include_private;

    rb_scan_args(argc, argv, "12", &mid, &include_super, &include_private);
    if (argc < 3) {
        include_private = Qfalse;
        if (argc < 2) {
            include_super = Qtrue;
        }
    }

    rb_method_visibility_t visi = check_definition_visibility(mod, mid, RTEST(include_super));
    switch (visi) {
      case METHOD_VISI_UNDEF:
        return Qfalse;
      case METHOD_VISI_PUBLIC:
      case METHOD_VISI_PROTECTED:
        return Qtrue;
      case METHOD_VISI_PRIVATE:
        return RBOOL(RTEST(include_private));
      default:
        UNREACHABLE_RETURN(Qundef);
    }
}

Returns true if the named method is defined by mod. If inherit is set, the lookup will also search mod‘s ancestors. By default only public and protected methods are matched, but if include_all is set the lookup will also consider private methods. String arguments are converted to symbols.

module A
  def method1()  end
  def protected_method1()  end
  protected :protected_method1
end
class B
  def method2()  end
  def private_method2()  end
  private :private_method2
end
class C < B
  include A
  def method3()  end
end

A.method_defined? :method1                       #=> true
C.method_defined? "method1"                      #=> true
C.method_defined? "method2"                      #=> true
C.method_defined? "method2", true                #=> true
C.method_defined? "method2", false               #=> false
C.method_defined? "method3"                      #=> true
C.method_defined? "protected_method1"            #=> true
C.method_defined? "method4"                      #=> false
C.method_defined? "private_method2"              #=> false
C.method_defined? "private_method2", true, true  #=> true
C.method_defined? "private_method2", false, true #=> false

static VALUE
rb_mod_module_eval_internal(int argc, const VALUE *argv, VALUE mod)
{
    return specific_eval(argc, argv, mod, FALSE, RB_PASS_CALLED_KEYWORDS);
}

Evaluates the string or block in the context of self. Returns the result of the last expression.

When string is given, evaluates the given string in the context of self:

class Foo; end

Foo.module_eval("def greeting = puts 'hello'")

Foo.new.greeting # => "hello"

If the optional filename is given, it will be used as the filename of the evaluation (for __FILE__ and errors). Otherwise, it will default to (eval at __FILE__:__LINE__) where __FILE__ and __LINE__ are the filename and line number of the caller, respectively:

class Foo; end

Foo.module_eval("puts __FILE__") # => "(eval at ../test.rb:3)"
Foo.module_eval("puts __FILE__", "foobar.rb") # => "foobar.rb"

If the optional lineno is given, it will be used as the line number of the evaluation (for __LINE__ and errors). Otherwise, it will default to 1:

class Foo; end

Foo.module_eval("puts __LINE__") # => 1
Foo.module_eval("puts __LINE__", nil, 10) # => 10

When a block is given, evaluates the block in the context of self:

class Foo; end

Foo.module_eval do
  def greeting = puts "hello"
end

Foo.new.greeting

However, constant and class variable lookup differs between string and block. When string is given, constant and class variables are looked up in the context of self. When a block is given, the context of the lookup is not changed:

class Foo
  GREETING = "hello"
end

Foo.module_eval("puts GREETING") # => "hello"

Foo.module_eval { puts GREETING } # => NameError: uninitialized constant GREETING

static VALUE
rb_mod_module_exec_internal(int argc, const VALUE *argv, VALUE mod)
{
    return yield_under(mod, FALSE, argc, argv, RB_PASS_CALLED_KEYWORDS);
}

Evaluates the given block in the context of the class/module. The method defined in the block will belong to the receiver. Any arguments passed to the method will be passed to the block. This can be used if the block needs to access instance variables.

class Thing
end
Thing.class_exec{
  def hello() "Hello there!" end
}
puts Thing.new.hello()

produces:

Hello there!

VALUE
rb_mod_name(VALUE mod)
{
    // YJIT needs this function to not allocate.
    bool permanent;
    return classname(mod, &permanent);
}

Returns the name of the module mod. Returns nil for anonymous modules.

static VALUE
rb_mod_prepend(int argc, VALUE *argv, VALUE module)
{
    int i;
    ID id_prepend_features, id_prepended;

    if (BUILTIN_TYPE(module) == T_MODULE && FL_TEST(module, RMODULE_IS_REFINEMENT)) {
        rb_raise(rb_eTypeError, "Refinement#prepend has been removed");
    }

    CONST_ID(id_prepend_features, "prepend_features");
    CONST_ID(id_prepended, "prepended");

    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    for (i = 0; i < argc; i++) {
        Check_Type(argv[i], T_MODULE);
        if (FL_TEST(argv[i], RMODULE_IS_REFINEMENT)) {
            rb_raise(rb_eTypeError, "Cannot prepend refinement");
        }
    }
    while (argc--) {
        rb_funcallv_uncached(argv[argc], id_prepend_features, 1, &module);
        rb_funcallv_uncached(argv[argc], id_prepended, 1, &module);
    }
    return module;
}

Invokes Module.prepend_features on each parameter in reverse order.

static VALUE
rb_mod_private_method(int argc, VALUE *argv, VALUE obj)
{
    set_method_visibility(rb_singleton_class(obj), argc, argv, METHOD_VISI_PRIVATE);
    return obj;
}

Makes existing class methods private. Often used to hide the default constructor new.

String arguments are converted to symbols. An Array of Symbols and/or Strings is also accepted.

class SimpleSingleton  # Not thread safe
  private_class_method :new
  def SimpleSingleton.create(*args, &block)
    @me = new(*args, &block) if ! @me
    @me
  end
end

VALUE
rb_mod_private_constant(int argc, const VALUE *argv, VALUE obj)
{
    set_const_visibility(obj, argc, argv, CONST_PRIVATE, CONST_VISIBILITY_MASK);
    return obj;
}

Makes a list of existing constants private.

VALUE
rb_class_private_instance_methods(int argc, const VALUE *argv, VALUE mod)
{
    return class_instance_method_list(argc, argv, mod, 0, ins_methods_priv_i);
}

Returns a list of the private instance methods defined in mod. If the optional parameter is false, the methods of any ancestors are not included.

module Mod
  def method1()  end
  private :method1
  def method2()  end
end
Mod.instance_methods           #=> [:method2]
Mod.private_instance_methods   #=> [:method1]

static VALUE
rb_mod_private_method_defined(int argc, VALUE *argv, VALUE mod)
{
    return check_definition(mod, argc, argv, METHOD_VISI_PRIVATE);
}

Returns true if the named private method is defined by mod. If inherit is set, the lookup will also search mod‘s ancestors. String arguments are converted to symbols.

module A
  def method1()  end
end
class B
  private
  def method2()  end
end
class C < B
  include A
  def method3()  end
end

A.method_defined? :method1                   #=> true
C.private_method_defined? "method1"          #=> false
C.private_method_defined? "method2"          #=> true
C.private_method_defined? "method2", true    #=> true
C.private_method_defined? "method2", false   #=> false
C.method_defined? "method2"                  #=> false

VALUE
rb_class_protected_instance_methods(int argc, const VALUE *argv, VALUE mod)
{
    return class_instance_method_list(argc, argv, mod, 0, ins_methods_prot_i);
}

Returns a list of the protected instance methods defined in mod. If the optional parameter is false, the methods of any ancestors are not included.

static VALUE
rb_mod_protected_method_defined(int argc, VALUE *argv, VALUE mod)
{
    return check_definition(mod, argc, argv, METHOD_VISI_PROTECTED);
}

Returns true if the named protected method is defined mod. If inherit is set, the lookup will also search mod‘s ancestors. String arguments are converted to symbols.

module A
  def method1()  end
end
class B
  protected
  def method2()  end
end
class C < B
  include A
  def method3()  end
end

A.method_defined? :method1                    #=> true
C.protected_method_defined? "method1"         #=> false
C.protected_method_defined? "method2"         #=> true
C.protected_method_defined? "method2", true   #=> true
C.protected_method_defined? "method2", false  #=> false
C.method_defined? "method2"                   #=> true

static VALUE
rb_mod_public_method(int argc, VALUE *argv, VALUE obj)
{
    set_method_visibility(rb_singleton_class(obj), argc, argv, METHOD_VISI_PUBLIC);
    return obj;
}

Makes a list of existing class methods public.

String arguments are converted to symbols. An Array of Symbols and/or Strings is also accepted.

VALUE
rb_mod_public_constant(int argc, const VALUE *argv, VALUE obj)
{
    set_const_visibility(obj, argc, argv, CONST_PUBLIC, CONST_VISIBILITY_MASK);
    return obj;
}

Makes a list of existing constants public.

static VALUE
rb_mod_public_instance_method(VALUE mod, VALUE vid)
{
    ID id = rb_check_id(&vid);
    if (!id) {
        rb_method_name_error(mod, vid);
    }
    return mnew_unbound(mod, id, rb_cUnboundMethod, TRUE);
}

Similar to instance_method, searches public method only.

VALUE
rb_class_public_instance_methods(int argc, const VALUE *argv, VALUE mod)
{
    return class_instance_method_list(argc, argv, mod, 0, ins_methods_pub_i);
}

Returns a list of the public instance methods defined in mod. If the optional parameter is false, the methods of any ancestors are not included.

static VALUE
rb_mod_public_method_defined(int argc, VALUE *argv, VALUE mod)
{
    return check_definition(mod, argc, argv, METHOD_VISI_PUBLIC);
}

Returns true if the named public method is defined by mod. If inherit is set, the lookup will also search mod‘s ancestors. String arguments are converted to symbols.

module A
  def method1()  end
end
class B
  protected
  def method2()  end
end
class C < B
  include A
  def method3()  end
end

A.method_defined? :method1                 #=> true
C.public_method_defined? "method1"         #=> true
C.public_method_defined? "method1", true   #=> true
C.public_method_defined? "method1", false  #=> true
C.public_method_defined? "method2"         #=> false
C.method_defined? "method2"                #=> true

static VALUE
mod_refinements(VALUE self)
{
    ID id_refinements;
    VALUE refinements;

    CONST_ID(id_refinements, "__refinements__");
    refinements = rb_attr_get(self, id_refinements);
    if (NIL_P(refinements)) {
        return rb_ary_new();
    }
    return rb_hash_values(refinements);
}

Returns an array of Refinement defined within the receiver.

module A
  refine Integer do
  end

  refine String do
  end
end

p A.refinements

produces:

[#<refinement:Integer@A>, #<refinement:String@A>]

VALUE
rb_mod_remove_cvar(VALUE mod, VALUE name)
{
    const ID id = id_for_var_message(mod, name, class, "wrong class variable name %1$s");
    st_data_t val;

    if (!id) {
        goto not_defined;
    }
    rb_check_frozen(mod);
    cvar_set_ractor_check(mod, id);
    val = rb_ivar_delete(mod, id, Qundef);
    if (!UNDEF_P(val)) {
        return (VALUE)val;
    }
    if (rb_cvar_defined(mod, id)) {
        rb_name_err_raise("cannot remove %1$s for %2$s", mod, ID2SYM(id));
    }
  not_defined:
    rb_name_err_raise("class variable %1$s not defined for %2$s",
                      mod, name);
    UNREACHABLE_RETURN(Qundef);
}

Removes the named class variable from the receiver, returning that variable’s value.

class Example
  @@var = 99
  puts remove_class_variable(:@@var)
  p(defined? @@var)
end

produces:

99
nil

static VALUE
rb_mod_remove_method(int argc, VALUE *argv, VALUE mod)
{
    int i;

    for (i = 0; i < argc; i++) {
        VALUE v = argv[i];
        ID id = rb_check_id(&v);
        if (!id) {
            rb_name_err_raise("method '%1$s' not defined in %2$s",
                              mod, v);
        }
        remove_method(mod, id);
    }
    return mod;
}

Removes the method identified by symbol from the current class. For an example, see Module#undef_method. String arguments are converted to symbols.

VALUE
rb_mod_set_temporary_name(VALUE mod, VALUE name)
{
    rb_class_owner_check(mod);

    // We don't allow setting the name if the classpath is already permanent:
    if (RCLASS_PERMANENT_CLASSPATH_P(mod)) {
        rb_raise(rb_eRuntimeError, "can't change permanent name");
    }

    if (NIL_P(name)) {
        // Set the temporary classpath to NULL (anonymous):
        RB_VM_LOCKING() {
            set_sub_temporary_name(mod, 0);
        }
    }
    else {
        // Ensure the name is a string:
        StringValue(name);

        if (RSTRING_LEN(name) == 0) {
            rb_raise(rb_eArgError, "empty class/module name");
        }

        if (is_constant_path(name)) {
            rb_raise(rb_eArgError, "the temporary name must not be a constant path to avoid confusion");
        }

        name = rb_str_new_frozen(name);
        RB_OBJ_SET_SHAREABLE(name);

        // Set the temporary classpath to the given name:
        RB_VM_LOCKING() {
            set_sub_temporary_name(mod, name);
        }
    }

    return mod;
}

Sets the temporary name of the module. This name is reflected in introspection of the module and the values that are related to it, such as instances, constants, and methods.

The name should be nil or a non-empty string that is not a valid constant path (to avoid confusing between permanent and temporary names).

The method can be useful to distinguish dynamically generated classes and modules without assigning them to constants.

If the module is given a permanent name by assigning it to a constant, the temporary name is discarded. A temporary name can’t be assigned to modules that have a permanent name.

If the given name is nil, the module becomes anonymous again.

Example:

m = Module.new # => #<Module:0x0000000102c68f38>
m.name #=> nil

m.set_temporary_name("fake_name") # => fake_name
m.name #=> "fake_name"

m.set_temporary_name(nil) # => #<Module:0x0000000102c68f38>
m.name #=> nil

c = Class.new
c.set_temporary_name("MyClass(with description)") # => MyClass(with description)

c.new # => #<MyClass(with description):0x0....>

c::M = m
c::M.name #=> "MyClass(with description)::M"

# Assigning to a constant replaces the name with a permanent one
C = c

C.name #=> "C"
C::M.name #=> "C::M"
c.new # => #<C:0x0....>

static VALUE
rb_mod_singleton_p(VALUE klass)
{
    return RBOOL(RCLASS_SINGLETON_P(klass));
}

Returns true if mod is a singleton class or false if it is an ordinary class or module.

class C
end
C.singleton_class?                  #=> false
C.singleton_class.singleton_class?  #=> true

VALUE
rb_mod_to_s(VALUE klass)
{
    ID id_defined_at;
    VALUE refined_class, defined_at;

    if (RCLASS_SINGLETON_P(klass)) {
        VALUE s = rb_usascii_str_new2("#<Class:");
        VALUE v = RCLASS_ATTACHED_OBJECT(klass);

        if (CLASS_OR_MODULE_P(v)) {
            rb_str_append(s, rb_inspect(v));
        }
        else {
            rb_str_append(s, rb_any_to_s(v));
        }
        rb_str_cat2(s, ">");

        return s;
    }
    refined_class = rb_refinement_module_get_refined_class(klass);
    if (!NIL_P(refined_class)) {
        VALUE s = rb_usascii_str_new2("#<refinement:");

        rb_str_concat(s, rb_inspect(refined_class));
        rb_str_cat2(s, "@");
        CONST_ID(id_defined_at, "__defined_at__");
        defined_at = rb_attr_get(klass, id_defined_at);
        rb_str_concat(s, rb_inspect(defined_at));
        rb_str_cat2(s, ">");
        return s;
    }
    return rb_class_name(klass);
}

Returns a string representing this module or class. For basic classes and modules, this is the name. For singletons, we show information on the thing we’re attached to as well.

static VALUE
rb_mod_undef_method(int argc, VALUE *argv, VALUE mod)
{
    int i;
    for (i = 0; i < argc; i++) {
        VALUE v = argv[i];
        ID id = rb_check_id(&v);
        if (!id) {
            rb_method_name_error(mod, v);
        }
        rb_undef(mod, id);
    }
    return mod;
}

Prevents the current class from responding to calls to the named method. Contrast this with remove_method, which deletes the method from the particular class; Ruby will still search superclasses and mixed-in modules for a possible receiver. String arguments are converted to symbols.

class Parent
  def hello
    puts "In parent"
  end
end
class Child < Parent
  def hello
    puts "In child"
  end
end

c = Child.new
c.hello

class Child
  remove_method :hello  # remove from child, still in parent
end
c.hello

class Child
  undef_method :hello   # prevent any calls to 'hello'
end
c.hello

produces:

In child
In parent
prog.rb:23: undefined method 'hello' for #<Child:0x401b3bb4> (NoMethodError)

VALUE
rb_class_undefined_instance_methods(VALUE mod)
{
    VALUE include_super = Qfalse;
    return class_instance_method_list(1, &include_super, mod, 0, ins_methods_undef_i);
}

Returns a list of the undefined instance methods defined in mod. The undefined methods of any ancestors are not included.

static VALUE
rb_mod_append_features(VALUE module, VALUE include)
{
    if (!CLASS_OR_MODULE_P(include)) {
        Check_Type(include, T_CLASS);
    }
    rb_include_module(include, module);

    return module;
}

When this module is included in another, Ruby calls append_features in this module, passing it the receiving module in mod. Ruby’s default implementation is to add the constants, methods, and module variables of this module to mod if this module has not already been added to mod or one of its ancestors. See also Module#include.

#define rb_obj_mod_const_added rb_obj_dummy1

Invoked as a callback whenever a constant is assigned on the receiver

module Chatty
  def self.const_added(const_name)
    super
    puts "Added #{const_name.inspect}"
  end
  FOO = 1
end

produces:

Added :FOO

If we define a class using the class keyword, const_added runs before inherited:

module M
  def self.const_added(const_name)
    super
    p :const_added
  end

  parent = Class.new do
    def self.inherited(subclass)
      super
      p :inherited
    end
  end

  class Child < parent
  end
end

produces:

:const_added
:inherited

static VALUE
rb_mod_extend_object(VALUE mod, VALUE obj)
{
    rb_extend_object(obj, mod);
    return obj;
}

Extends the specified object by adding this module’s constants and methods (which are added as singleton methods). This is the callback method used by Object#extend.

module Picky
  def Picky.extend_object(o)
    if String === o
      puts "Can't add Picky to a String"
    else
      puts "Picky added to #{o.class}"
      super
    end
  end
end
(s = Array.new).extend Picky  # Call Object.extend
(s = "quick brown fox").extend Picky

produces:

Picky added to Array
Can't add Picky to a String

#define rb_obj_mod_extended rb_obj_dummy1

The equivalent of included, but for extended modules.

module A
  def self.extended(mod)
    puts "#{self} extended in #{mod}"
  end
end
module Enumerable
  extend A
end
 # => prints "A extended in Enumerable"

#define rb_obj_mod_included rb_obj_dummy1

Callback invoked whenever the receiver is included in another module or class. This should be used in preference to Module.append_features if your code wants to perform some action when a module is included in another.

module A
  def A.included(mod)
    puts "#{self} included in #{mod}"
  end
end
module Enumerable
  include A
end
 # => prints "A included in Enumerable"

#define rb_obj_mod_method_added rb_obj_dummy1

Invoked as a callback whenever an instance method is added to the receiver.

module Chatty
  def self.method_added(method_name)
    puts "Adding #{method_name.inspect}"
  end
  def self.some_class_method() end
  def some_instance_method() end
end

produces:

Adding :some_instance_method

#define rb_obj_mod_method_removed rb_obj_dummy1

Invoked as a callback whenever an instance method is removed from the receiver.

module Chatty
  def self.method_removed(method_name)
    puts "Removing #{method_name.inspect}"
  end
  def self.some_class_method() end
  def some_instance_method() end
  class << self
    remove_method :some_class_method
  end
  remove_method :some_instance_method
end

produces:

Removing :some_instance_method

#define rb_obj_mod_method_undefined rb_obj_dummy1

Invoked as a callback whenever an instance method is undefined from the receiver.

module Chatty
  def self.method_undefined(method_name)
    puts "Undefining #{method_name.inspect}"
  end
  def self.some_class_method() end
  def some_instance_method() end
  class << self
    undef_method :some_class_method
  end
  undef_method :some_instance_method
end

produces:

Undefining :some_instance_method

static VALUE
rb_mod_modfunc(int argc, VALUE *argv, VALUE module)
{
    int i;
    ID id;
    const rb_method_entry_t *me;

    if (!RB_TYPE_P(module, T_MODULE)) {
        rb_raise(rb_eTypeError, "module_function must be called for modules");
    }

    if (argc == 0) {
        rb_scope_module_func_set();
        return Qnil;
    }

    set_method_visibility(module, argc, argv, METHOD_VISI_PRIVATE);

    for (i = 0; i < argc; i++) {
        VALUE m = module;

        id = rb_to_id(argv[i]);
        for (;;) {
            me = search_method(m, id, 0);
            if (me == 0) {
                me = search_method(rb_cObject, id, 0);
            }
            if (UNDEFINED_METHOD_ENTRY_P(me)) {
                rb_print_undef(module, id, METHOD_VISI_UNDEF);
            }
            if (me->def->type != VM_METHOD_TYPE_ZSUPER) {
                break; /* normal case: need not to follow 'super' link */
            }
            m = RCLASS_SUPER(m);
            if (!m)
                break;
        }
        rb_method_entry_set(rb_singleton_class(module), id, me, METHOD_VISI_PUBLIC);
    }
    if (argc == 1) {
        return argv[0];
    }
    return rb_ary_new_from_values(argc, argv);
}

Creates module functions for the named methods. These functions may be called with the module as a receiver, and also become available as instance methods to classes that mix in the module. Module functions are copies of the original, and so may be changed independently. The instance-method versions are made private. String arguments are converted to symbols. If a single argument is passed, it is returned. If no argument is passed, nil is returned. If multiple arguments are passed, the arguments are returned as an array.

module Mod
  def one
    "This is one"
  end
  module_function :one
end
class Cls
  include Mod
  def call_one
    one
  end
end
Mod.one     #=> "This is one"
c = Cls.new
c.call_one  #=> "This is one"
module Mod
  def one
    "This is the new one"
  end
end
Mod.one     #=> "This is one"
c.call_one  #=> "This is the new one"

If used with no arguments, subsequently defined methods become module functions:

module Mod
  module_function

  def two
    "This is two"
  end
end
Mod.two  #=> "This is two"

static VALUE
rb_mod_prepend_features(VALUE module, VALUE prepend)
{
    if (!CLASS_OR_MODULE_P(prepend)) {
        Check_Type(prepend, T_CLASS);
    }
    rb_prepend_module(prepend, module);

    return module;
}

When this module is prepended in another, Ruby calls prepend_features in this module, passing it the receiving module in mod. Ruby’s default implementation is to overlay the constants, methods, and module variables of this module to mod if this module has not already been added to mod or one of its ancestors. See also Module#prepend.

#define rb_obj_mod_prepended rb_obj_dummy1

The equivalent of included, but for prepended modules.

module A
  def self.prepended(mod)
    puts "#{self} prepended to #{mod}"
  end
end
module Enumerable
  prepend A
end
 # => prints "A prepended to Enumerable"

static VALUE
rb_mod_private(int argc, VALUE *argv, VALUE module)
{
    return set_visibility(argc, argv, module, METHOD_VISI_PRIVATE);
}

With no arguments, sets the default visibility for subsequently defined methods to private. With arguments, sets the named methods to have private visibility. String arguments are converted to symbols. An Array of Symbols and/or Strings is also accepted. If a single argument is passed, it is returned. If no argument is passed, nil is returned. If multiple arguments are passed, the arguments are returned as an array.

module Mod
  def a()  end
  def b()  end
  private
  def c()  end
  private :a
end
Mod.private_instance_methods   #=> [:a, :c]

Note that to show a private method on RDoc, use :doc:.

static VALUE
rb_mod_protected(int argc, VALUE *argv, VALUE module)
{
    return set_visibility(argc, argv, module, METHOD_VISI_PROTECTED);
}

Sets the visibility of a section or of a list of method names as protected. Accepts no arguments, a splat of method names (symbols or strings) or an array of method names. Returns the arguments that it received.

Important difference between protected in other languages

Protected methods in Ruby are different from other languages such as Java, where methods are marked as protected to give access to subclasses. In Ruby, subclasses already have access to all methods defined in the parent class, even private ones.

Marking a method as protected allows different objects of the same class to call it.

One use case is for comparison methods, such as ==, if we want to expose a method for comparison between objects of the same class without making the method public to objects of other classes.

Performance considerations

Protected methods are slower than others because they can’t use inline cache.

Example

class Account
  # Mark balance as protected, so that we can compare between accounts
  # without making it public.
  attr_reader :balance
  protected :balance

  def initialize(balance)
    @balance = balance
  end

  def >(other)
    # The invocation to `other.balance` is allowed because `other` is a
    # different object of the same class (Account).
    balance > other.balance
  end
end

account1 = Account.new(100)
account2 = Account.new(50)

account1 > account2  # => true (works)
account1.balance     # => NoMethodError (fails because balance is not public)

To show a private method on RDoc, use :doc: instead of this.

static VALUE
rb_mod_public(int argc, VALUE *argv, VALUE module)
{
    return set_visibility(argc, argv, module, METHOD_VISI_PUBLIC);
}

With no arguments, sets the default visibility for subsequently defined methods to public. With arguments, sets the named methods to have public visibility. String arguments are converted to symbols. An Array of Symbols and/or Strings is also accepted. If a single argument is passed, it is returned. If no argument is passed, nil is returned. If multiple arguments are passed, the arguments are returned as an array.

static VALUE
rb_mod_refine(VALUE module, VALUE klass)
{
    /* module is the receiver of #refine, klass is a module to be refined (`mod` in the doc) */
    rb_thread_t *th = GET_THREAD();
    VALUE block_handler = rb_vm_frame_block_handler(th->ec->cfp);
    struct rb_refinements_data data;

    if (block_handler == VM_BLOCK_HANDLER_NONE) {
        rb_raise(rb_eArgError, "no block given");
    }
    if (vm_block_handler_type(block_handler) != block_handler_type_iseq) {
        rb_raise(rb_eArgError, "can't pass a Proc as a block to Module#refine");
    }

    ensure_class_or_module(klass);

    // refine installs refined method entries into the target's method table, and
    // rb_refinement_setup writes the refinement tables into the receiver
    rb_class_owner_check(module);
    rb_class_owner_check(klass);

    rb_refinement_setup(&data, module, klass);

    rb_yield_refine_block(data.refinement, data.refinements);
    return data.refinement;
}

Refine mod in the receiver.

Returns a module, where refined methods are defined.

VALUE
rb_mod_remove_const(VALUE mod, VALUE name)
{
    const ID id = id_for_var(mod, name, a, constant);

    if (!id) {
        undefined_constant(mod, name);
    }
    return rb_const_remove(mod, id);
}

Removes the definition of the given constant, returning that constant’s previous value. If that constant referred to a module, this will not change that module’s name and can lead to confusion.

static VALUE
rb_mod_ruby2_keywords(int argc, VALUE *argv, VALUE module)
{
    int i;
    VALUE origin_class = RCLASS_ORIGIN(module);

    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    rb_check_frozen(module);
    rb_class_owner_check(module);

    for (i = 0; i < argc; i++) {
        VALUE v = argv[i];
        ID name = rb_check_id(&v);
        rb_method_entry_t *me;
        VALUE defined_class;

        if (!name) {
            rb_print_undef_str(module, v);
        }

        me = search_method(origin_class, name, &defined_class);
        if (!me && RB_TYPE_P(module, T_MODULE)) {
            me = search_method(rb_cObject, name, &defined_class);
        }

        if (UNDEFINED_METHOD_ENTRY_P(me) ||
            UNDEFINED_REFINED_METHOD_P(me->def)) {
            rb_print_undef(module, name, METHOD_VISI_UNDEF);
        }

        if (module == defined_class || origin_class == defined_class) {
            switch (me->def->type) {
              case VM_METHOD_TYPE_ISEQ:
                if (ISEQ_BODY(me->def->body.iseq.iseqptr)->param.flags.has_rest &&
                        !ISEQ_BODY(me->def->body.iseq.iseqptr)->param.flags.has_post &&
                        !ISEQ_BODY(me->def->body.iseq.iseqptr)->param.flags.has_kw &&
                        !ISEQ_BODY(me->def->body.iseq.iseqptr)->param.flags.has_kwrest) {
                    ISEQ_BODY(me->def->body.iseq.iseqptr)->param.flags.ruby2_keywords = 1;
                    rb_clear_method_cache(module, name);
                }
                else {
                    rb_warn("Skipping set of ruby2_keywords flag for %"PRIsVALUE" (method accepts keywords or post arguments or method does not accept argument splat)", QUOTE_ID(name));
                }
                break;
              case VM_METHOD_TYPE_BMETHOD: {
                VALUE procval = me->def->body.bmethod.proc;
                if (vm_block_handler_type(procval) == block_handler_type_proc) {
                    procval = vm_proc_to_block_handler(VM_BH_TO_PROC(procval));
                }

                if (vm_block_handler_type(procval) == block_handler_type_iseq) {
                    const struct rb_captured_block *captured = VM_BH_TO_ISEQ_BLOCK(procval);
                    const rb_iseq_t *iseq = rb_iseq_check(captured->code.iseq);
                    if (ISEQ_BODY(iseq)->param.flags.has_rest &&
                            !ISEQ_BODY(iseq)->param.flags.has_post &&
                            !ISEQ_BODY(iseq)->param.flags.has_kw &&
                            !ISEQ_BODY(iseq)->param.flags.has_kwrest) {
                        ISEQ_BODY(iseq)->param.flags.ruby2_keywords = 1;
                        rb_clear_method_cache(module, name);
                    }
                    else {
                        rb_warn("Skipping set of ruby2_keywords flag for %"PRIsVALUE" (method accepts keywords or post arguments or method does not accept argument splat)", QUOTE_ID(name));
                    }
                    break;
                }
              }
              /* fallthrough */
              default:
                rb_warn("Skipping set of ruby2_keywords flag for %"PRIsVALUE" (method not defined in Ruby)", QUOTE_ID(name));
                break;
            }
        }
        else {
            rb_warn("Skipping set of ruby2_keywords flag for %"PRIsVALUE" (can only set in method defining module)", QUOTE_ID(name));
        }
    }
    return Qnil;
}

Deprecated: will be removed in Ruby 4.4. Use ... argument forwarding or other delegation styles instead; they work correctly on Ruby 3.0 and later. See bugs.ruby-lang.org/issues/22205 for the schedule.

For the given method names, marks the method as passing keywords through a normal argument splat. This should only be called on methods that accept an argument splat (*args) but not explicit keywords or a keyword splat. It marks the method such that if the method is called with keyword arguments, the final hash argument is marked with a special flag such that if it is the final element of a normal argument splat to another method call, and that method call does not include explicit keywords or a keyword splat, the final element is interpreted as keywords. In other words, keywords will be passed through the method to other methods.

This should only be used for methods that delegate keywords to another method, and only for backwards compatibility with Ruby versions before 3.0. See www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/ for details on why ruby2_keywords exists and when and how to use it.

static VALUE
mod_using(VALUE self, VALUE module)
{
    rb_control_frame_t *prev_cfp = previous_frame(GET_EC());

    if (prev_frame_func()) {
        rb_raise(rb_eRuntimeError,
                 "Module#using is not permitted in methods");
    }
    if (prev_cfp && prev_cfp->self != self) {
        rb_raise(rb_eRuntimeError, "Module#using is not called on self");
    }
    if (rb_block_given_p()) {
        ignored_block(module, "Module#");
    }
    check_not_refined_proc_scope("Module#using");
    rb_using_module(rb_vm_cref_replace_with_duplicated_cref(), module);
    return self;
}

Import class refinements from module into the current class or module definition.