如何避免在TypeScript，Angular2的派生类中重复基类构造函数参数？

Question

@Injectable()
export class APIService {
  constructor(private http: Http) {
  }

}


@Injectable()
export class CourseAPIService extends APIService{

  constructor(private http2: Http){
    super(http2);
  }
}

I have baseclass as APIService having Http as constructor parameter unfortunately I have to pass it again in child class CourseAPIService. Please help me if any soln ...?

Answer 1

You can remove the constructor completely from CourseAPIService if you are not using the private http2 property in CourseAPIService .

If you do want to use the Http service in CourseAPIService , you can mark the http property as protected in APIService and share it with CourseAPIService .

@Injectable()
export class APIService {
  constructor(protected http: Http) {
  }
}

However if you define a constructor for CourseAPIService you must call its base class constructor with super passing necessary arguments.

Answer 2

AFAIK, the answer is No. You need call super() from derived class. So, if your base class has dependencies, your derived class must inject same dependencies and pass to super() method.