Angular: Extending Services and Passing Parameters

So after some good work by CH Buckingham I've resolved that doing it the "typical" way is impossible.

Angular2 simply takes over the constructor() function with the injector. What does work however is make an alternate "init" function that you can then pass parameters to.

@Injectable()
export class ParentService {
  root:string = "This content comes from: ";
  myString:string = "The Parent";
  resultString:string;
  constructor(){
    this.init();
  }
  init() {
    this.resultString = this.root + this.myString;
  }
}


@Injectable()
export class ChildService extends ParentService {
  constructor(){
    super();
  }
  init() {
    this.myString = "The Child";
    super.init();
  }
}

In this way you can set values on the child object or pass them through to the parent.

Plunker of this in action

Here is another way to extend a service in angular2 which works with the DI. The child service cannot use the same parameter name for injectable services used by the parent, hence the reason for anotherHttp parameter name.

The parent service:

@Injectable()
export class GenericStore {
   ....
   constructor(public config:GenericConfig,private http:Http) {
        ....
   }
   ....
}

The child service:

const DEFAULT_CONFIG:GenericConfig = { ... };
@Injectable()
export class ConfigStore extends GenericStore {
   ....
   constructor(private anotherHttp:Http) {
        super(DEFAULT_CONFIG,anotherHttp);
   }
   ....
}