After reading this section about component interaction — I've noticed that there is another way of communicating from child to parent ( which wasn't really documented there) :

It turns out that if I have a parent class :

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>
      <my-item></my-item>
    </div>
  `,
})
export class App {
  name:string;
  go1()
   {
     alert(2)
   }
  constructor() {}
}

And in the child component - I Inject a parent type into the ctor :

@Component({
  selector: 'my-item',
  template: `
    <div>
     <input type="button" value='invoke parent method' (click) = "myGo()"/>
    </div>
  `,
})
  class MyItem {
  name:string;
  private parent1 : App; 

  myGo()
  {
    this.parent1.go1()    //<--- access is available here
  } 

  constructor(private parent1 : App) 
   {
    this.parent1 = parent1; //<------------ manually, unlike service
    this.name = `Angular! v${VERSION.full}`
   }
}

Then Angular sees that i'm trying to inject a parent type class and it gives me access to it.

The click works of course.

Question:

Beside other alternatives which I already know , is it documented anywhere ? or is it just a feature that I can't rely on it

plnkr