Injectable

Decorator that marks a class as available to be provided and injected as a dependency.

Option	Description
providedIn	Determines which injectors will provide the injectable, by either associating it with an @NgModule or other InjectorType, or by specifying that this injectable should be provided in the 'root' injector, which will be the application-level injector in most apps.

See also

• Introduction to Services and DI

• Dependency Injection Guide

Options

providedIn
Determines which injectors will provide the injectable, by either associating it with an @NgModule or other InjectorType, or by specifying that this injectable should be provided in the 'root' injector, which will be the application-level injector in most apps.
providedIn: Type<any> | 'root' | null

Usage notes

Marking a class with @Injectable ensures that the compiler will generate the necessary metadata to create the class's dependencies when the class is injected.

The following example shows how a service class is properly marked so that a supporting service can be injected upon creation.

@Injectable()
class UsefulService {
}

@Injectable()
class NeedsService {
  constructor(public service: UsefulService) {}
}

const injector = Injector.create({
  providers: [
    {provide: NeedsService, deps: [UsefulService]}, {provide: UsefulService, deps: []}
  ]
});
expect(injector.get(NeedsService).service instanceof UsefulService).toBe(true);