GeezerVison is showing doc.rust-lang.org — Poll in std::task - Rust pub enum Poll<T> {
Ready(T),
Pending,
}
Expand descriptionIndicates whether a value is available or if the current task has been
scheduled to receive a wakeup instead.
This is returned by Future::poll.
Variants§Represents that a value is immediately ready.
Represents that a value is not ready yet.
When a function returns Pending, the function must also
ensure that the current task is scheduled to be awoken when
progress can be made.
Implementations§
Maps a Poll<T> to Poll<U> by applying a function to a contained value.
§Examples
Converts a Poll<String> into a Poll<usize>, consuming
the original:
let poll_some_string = Poll::Ready(String::from("Hello, World!"));
// `Poll::map` takes self *by value*, consuming `poll_some_string`
let poll_some_len = poll_some_string.map(|s| s.len());
assert_eq!(poll_some_len, Poll::Ready(13));
1.36.0 (const: 1.49.0) · SourceReturns true if the poll is a Poll::Ready value.
§Examples
let x: Poll<u32> = Poll::Ready(2);
assert_eq!(x.is_ready(), true);
let x: Poll<u32> = Poll::Pending;
assert_eq!(x.is_ready(), false);
1.36.0 (const: 1.49.0) · SourceReturns true if the poll is a Pending value.
§Examples
let x: Poll<u32> = Poll::Ready(2);
assert_eq!(x.is_pending(), false);
let x: Poll<u32> = Poll::Pending;
assert_eq!(x.is_pending(), true);
Maps a Poll<Result<T, E>> to Poll<Result<U, E>> by applying a
function to a contained Poll::Ready(Ok) value, leaving all other
variants untouched.
This function can be used to compose the results of two functions.
§Examples
let res: Poll<Result<u8, _>> = Poll::Ready("12".parse());
let squared = res.map_ok(|n| n * n);
assert_eq!(squared, Poll::Ready(Ok(144)));
Maps a Poll::Ready<Result<T, E>> to Poll::Ready<Result<T, U>> by
applying a function to a contained Poll::Ready(Err) value, leaving all other
variants untouched.
This function can be used to pass through a successful result while handling
an error.
§Examples
let res: Poll<Result<u8, _>> = Poll::Ready("oops".parse());
let res = res.map_err(|_| 0_u8);
assert_eq!(res, Poll::Ready(Err(0)));
Maps a Poll<Option<Result<T, E>>> to Poll<Option<Result<U, E>>> by
applying a function to a contained Poll::Ready(Some(Ok)) value,
leaving all other variants untouched.
This function can be used to compose the results of two functions.
§Examples
let res: Poll<Option<Result<u8, _>>> = Poll::Ready(Some("12".parse()));
let squared = res.map_ok(|n| n * n);
assert_eq!(squared, Poll::Ready(Some(Ok(144))));
Maps a Poll::Ready<Option<Result<T, E>>> to
Poll::Ready<Option<Result<T, F>>> by applying a function to a
contained Poll::Ready(Some(Err)) value, leaving all other variants
untouched.
This function can be used to pass through a successful result while handling
an error.
§Examples
let res: Poll<Option<Result<u8, _>>> = Poll::Ready(Some("oops".parse()));
let res = res.map_err(|_| 0_u8);
assert_eq!(res, Poll::Ready(Some(Err(0))));
Trait Implementations§
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Moves the value into a Poll::Ready to make a Poll<T>.
§Example
assert_eq!(Poll::from(true), Poll::Ready(true));
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) Constructs the type from a compatible Residual type. Read more
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) Constructs the type from a compatible Residual type. Read more
Compares and returns the maximum of two values. Read more
Compares and returns the minimum of two values. Read more
Restrict a value to a certain interval. Read more
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the
<= operator. Read more
Tests greater than (for self and other) and is used by the >
operator. Read more
Tests greater than or equal to (for self and other) and is used by
the >= operator. Read more
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) The type of the value produced by ? when not short-circuiting.
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) Constructs the type from its Output type. Read more
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) The type of the value produced by ? when not short-circuiting.
🔬This is a nightly-only experimental API. (try_trait_v2 #84277)
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) Constructs the type from its Output type. Read more
🔬This is a nightly-only experimental API. (try_trait_v2 #84277) Auto Trait Implementations§Blanket Implementations§
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
🔬This is a nightly-only experimental API. (clone_to_uninit #126799) Performs copy-assignment from self to dest. Read more
Converts to this type from the input type.
Returns the argument unchanged.
Calls U::from(self).
That is, this conversion is whatever the implementation of
From<T> for U chooses to do.
The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion. |