two way binding with safe navigation operator

Question

What is the best way to use two-way-binding (syntax-sugar) in Angular 2 with the safe navigation operator. I\'ve tried the following.

Answer 1

<input [ngModel]="x?.y?.z" (keyup)="changeMe($event.target.value)"> {{x?.y?.z}}

export class ParentCmp {
  x={y:{z:"a"}}
   changeMe(val)
    {
      console.log(val);
      this.x.y.z=val;
    }
}

http://plnkr.co/edit/ZBeSPqf4HUwLOeWSNfZJ?p=preview

Answer 2

You can split up- and downwards-binding like

<input [ngModel]="x?.y?.z" (ngModelChange)="x?.y?.z ? x.y.z = $event : null">