typescript - Child component events broadcast to parent

Question

I'd like to implement the common Angular 1.x pattern of having child directives within a parent directive in Angular 2. Here's my desired structure.

<foo>
  <bar>A</bar>
  <bar>B</bar>
  <bar>C</bar>
</foo>

I'd like for these Bar components to have click events that get emitted to the Foo component.

Here's my Foo so far:

@Component({
  selector: 'foo',
  template: `
    <div>
      <ng-content></ng-content>
    </div>
  `
})
export class Foo {
   @ContentChildren(Bar) items: QueryList<Bar>;
}

And here's my Bar:

@Component({
  selector: 'Bar',
  template: `
    <div (click)="clickity()">
      <ng-content></ng-content>
    </div>
  `
})
export class Bar {
  clickity() {
    console.log('Broadcast this to the parent please!');
  }
}

How do I go about notifying Foo whenever one of its Bars is clicked?

Answer 1

You can use a service to send data between components if you can't do it using @Output() decorator. Here's an example:

import {EventEmitter} from 'angular2/core';

export class EmitterService {
  private static _emitters: { [channel: string]: EventEmitter<any> } = {};
  static get(channel: string): EventEmitter<any> {
    if (!this._emitters[channel]) 
      this._emitters[channel] = new EventEmitter();
    return this._emitters[channel];
  }
}

You import it wherever you need to emit or subscribe to an event:

// foo.component.ts
import {EmitterService} from '../path/to/emitter.service'

class Foo {
  EmitterService.get("some_id").subscribe(data => console.log("some_id channel: ", data));
  EmitterService.get("other_id").subscribe(data => console.log("other_id channel: ", data));
}

// bar.component.ts
import {EmitterService} from '../path/to/emitter.service'

class Bar {

  onClick() {
    EmitterService.get("some_id").emit('you clicked!');
  }
  onScroll() {
    EmitterService.get("other_id").emit('you scrolled!');
  }
}

another example: plunker