Is host element event handler is set?

alert.ts

// index.ts
// (close) could be set or not
@Component({
  selector: 'app'
})
@View({
  template: `
  <alert (close)="closeAlert(i)">{{ alert1.msg }}</alert>
  <alert>{{ alert2.msg }}</alert>
  `,
  directives: [AlertComponent, coreDirectives]
})
class Hello{}

// alerts.ts
@Component({
  selector: 'alert',
  properties: ['type'],
  events: ['close'],
  lifecycle: [LifecycleEvent.onInit]
})
@View({
  template: `...doesn't care`,
  directives: [coreDirectives, CSSClass]
})
class AlertComponent{
  constructor(public el: ElementRef){
    // TODO: is there a better way to detect that event handler is set?
    this.closeable = el.nativeElement.getAttribute('(close)');
    this.close = new EventEmitter();
  }
}

Currently, there is no better way to detect if a listener is set. In theory though, you could have asked the event emitter if it had a listener. This is easy to implement, but I am not sure if it is a good idea.

We have the following mental model:

• Data flows into a component via property binding
• Data comes out via event binding

What you are asking for somewhat conflicts with this mental model. The event binding affects the state of the component. Don't you think it might be surprising for the user?

@vsavkin ok another quesion :)
if I want to implement http://angular-ui.github.io/bootstrap/#/buttons in
angular2 I can not use somewhat near ng-model, and have to update model like this

  <button (on-change)="(v) => {model.field =v;}"

or there are a way to implement

  <button ([ng-model])="model.field">

?
Thank in advance :)

about first question I will have to use something like '[(close)]' to feat into ng2 mental model

You can use <button [(ng-model)]="model.field">, you just need to defined a value accessor that will tell angular how to read and write a value to the button.

about first question I will have to use something like '[(close)]' to feat into ng2 mental model

[(a)] ="foo" just desugars to [a]="foo" (a)="foo=$event". I don't think it what you want. I was actually talking about the following: [show-close]="true" (close)="someHandler".

@vsavkin

you just need to defined a value accessor

yeap, debugged to this point yesterday,
now need to find about an interface of value accessor :)