How to detect change in model for input field from directive in angular2

Question

I have this code for a textarea, it is working great with the ngModel and updating live, however i would like my-custom-directive to know when the model bound to this textarea is changing.

How can i detect a model change for this textarea in the my-custom-directive?

  <textarea my-custom-directive class="green" [(ngModel)]="customertext"></textarea>

Answer 1

Update

@Directive({
  selector: 'xyz', 
  host: {'(ngModelChange)': 'doSomething($event)'}  
}) 
export class Xyz {
  doSomething(event){... }  
} 

Original

<textarea my-custom-directive class="green" [(ngModel)]="customertext"
    (ngModelChange)="doSomething($event) "></textarea>

[(ngModel)]="customertext"

is the short form of

[ngModel]="customertext" (ngModelChange)="customertext=$event"  

Answer 2

try add to your directive:

@HostListener('input') onInput() {
        console.log('on input');
}