@Inject

A constructor parameter decorator that specifies a custom provider of a dependency.

constructor(@Inject(ServiceToken) service: Service) {}

Example

The following example shows a class constructor that specifies a custom provider of a dependency using the parameter decorator.

class Engine {}

@Injectable()
class Car {
  constructor(@Inject('MyEngine') public engine: Engine) {}
}

const injector = ReflectiveInjector.resolveAndCreate([{provide: 'MyEngine', useClass: Engine}, Car]);

expect(injector.get(Car).engine instanceof Engine).toBe(true);

When @Inject() is not present, the Injector uses the type annotation of the parameter as the provider.

class Engine {}

@Injectable()
class Car {
  constructor(public engine: Engine) {
  }  // same as constructor(@Inject(Engine) engine:Engine)
}

const injector = ReflectiveInjector.resolveAndCreate([Engine, Car]);
expect(injector.get(Car).engine instanceof Engine).toBe(true);