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ClassProvider

interface

Configures the Injector to return an instance of useClass for a token.

interface ClassProvider extends ClassSansProvider {
  provide: any
  multi?: boolean

  // inherited from core/ClassSansProvider
  useClass: Type<any>
}

See also

Properties

Property Description
provide: any

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

multi?: boolean

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.

Usage notes

abstract class Shape {
  name!: string;
}

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

const injector = ReflectiveInjector.resolveAndCreate([{provide: Shape, useClass: 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 = ReflectiveInjector.resolveAndCreate(
    [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']);

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Licensed under the Creative Commons Attribution License 4.0.
https://angular.io/api/core/ClassProvider