Cookies concent notice

This site uses cookies from Google to deliver its services and to analyze traffic.
Learn more
Skip to main content
This site is no longer updated.Head to Angular.devHome
/

This is the archived documentation for Angular v17. Please visit angular.dev to see this page for the current version of Angular.

ClassProvider

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 = 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']);