Angular 2 ngModel in child component updates parent component property

We can use the [(x)] syntax in the parent template to achieve two-way databinding with the child. If we create an Output property with the name xChange, Angular will automatically update the parent property. We do need to emit() an event whenever the child changes the value however:

import {Component, EventEmitter, Input, Output} from 'angular2/core'

@Component({
    selector: 'child',
    template: `
        <p>Child sharedVar: {{sharedVar}}</p>
        <input [ngModel]="sharedVar" (ngModelChange)="change($event)">
    `
})
export class ChildComponent {
    @Input() sharedVar: string;
    @Output() sharedVarChange = new EventEmitter();
    change(newValue) {
      console.log('newvalue', newValue)
      this.sharedVar = newValue;
      this.sharedVarChange.emit(newValue);
    }
}

@Component({
    selector: 'parent',
    template: `
        <div>Parent sharedVarParent: {{sharedVarParent}}</div>
        <child [(sharedVar)]="sharedVarParent"></child>
    `,
    directives: [ChildComponent]
})
export class ParentComponent {
    sharedVarParent="hello";
    constructor() { console.clear(); }
}

Plunker

I used sharedVarParent in the ParentComponent just to demonstrate that the names don’t have to be the same in the parent and child.