GeezerVison

The World Wide Web, restored to 800 pixels of glory.

GeezerVison is showing angular.dev — ClassProvider • Angular

API

    
      interface ClassProvider extends ClassSansProvider {}

An injection token. (Typically an instance of Type or InjectionToken, but can be any).

When true, injector returns an array of instances. This is useful to allow multiple providers spread across many files to provide configuration information to a common token.

Class to instantiate for the token.

Usage Notes

abstract class Shape {
          name!: string;
        }

        class Square extends Shape {
          override name = 'square';
        }

        const injector = Injector.create({providers: [{provide: Shape, useValue: new Square()}]});

        const shape: Shape = injector.get(Shape);
        expect(shape.name).toEqual('square');
        expect(shape instanceof Square).toBe(true);

Note that following two providers are not equal:

class Greeting {
          salutation = 'Hello';
        }

        class FormalGreeting extends Greeting {
          override salutation = 'Greetings';
        }

        const injector = Injector.create({
          providers: [
            {provide: FormalGreeting, useClass: FormalGreeting},
            {provide: Greeting, useClass: FormalGreeting},
          ],
        });

        // The injector returns different instances.
        // See: {provide: ?, useExisting: ?} if you want the same instance.
        expect(injector.get(FormalGreeting)).not.toBe(injector.get(Greeting));

Multi-value example

const locale = new InjectionToken<string[]>('locale');
        const injector = Injector.create({
          providers: [
            {provide: locale, multi: true, useValue: 'en'},
            {provide: locale, multi: true, useValue: 'sk'},
          ],
        });

        const locales: string[] = injector.get(locale);
        expect(locales).toEqual(['en', 'sk']);

You are visitor 01402503 — GeezerVison does not store the pages you look up.
Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.