实际上，它是直接向前的：

• 提供令牌
• 提供服务
• 注入服务

示例：

// define the token
const token = new InjectionToken<string>('token');

// define a service depending on the token 
@Injectable()
export class MyService {
  // the token gets injected into the service
  constructor(@Inject(token) private token: string) {}

  getValue(): string {
    return this.token;
  }
}

@Component({
  selector: 'my-app',
  standalone: true,
  providers: [
    // provide token & service
    { provide: token, useValue: 'foobar'},
    MyService, 
  ],
  template: ``,
})
export class App {
  constructor(myService: MyService) {
    // enjoy
    console.log(myService.getValue());
  }
}

bootstrapApplication(App);