Angular2 - two way databinding on a component variable / component class property?

Question

In Angular2 (Beta 6) I have a component for a main menu.

I want to bind a boolean for wide or narrow. So

Answer 1

For two-way binding you need something like:

@Component({
    selector: 'menu',
    template: `
<button (click)="menuvisible = !menuvisible; menuvisibleChange.emit(menuvisible)">toggle</button>
<!-- or 
   <button (click)="toggleVisible()">toggle</button> -->
`,
    // HTTP_PROVIDERS should now be imports: [HttpModule] in @NgModule()
    providers: [/*HTTP_PROVIDERS*/, ApplicationService],
    // This should now be added to declarations and imports in @NgModule()
    // imports: [RouterModule, CommonModule, FormsModule]
    directives: [/*ROUTER_DIRECTIVES, FORM_DIRECTIVES, NgClass, NgForm*/]
})
export class MenuComponent implements OnInit {
    @Input() menuvisible:boolean;
    @Output() menuvisibleChange:EventEmitter<boolean> = new EventEmitter<boolean>();

    // toggleVisible() {
    //   this.menuvisible = !this.menuvisible;       
    //   this.menuvisibleChange.emit(this.menuvisible);
    // }
}

And use it like

@Component({
  selector: 'some-component',
  template: `
<menu [(menuvisible)]="menuVisibleInParent"></menu>
<div>visible: {{menuVisibleInParent}}</div>
`
  directives: [MenuComponent]
})
class SomeComponent {
  menuVisibleInParent: boolean;
}

Answer 2

I've created a short plunkr.

ngModel Like Two-Way-Databinding for components

You have at least two possibilities to to create a two way databinding for components

V1: With ngModel Like Syntax, there you have to create a @Output property with the same name line the @Input property + "Change" at the end of the @Output property name

@Input() name : string;
@Output() nameChange = new EventEmitter<string>(); 

with V1 you can now bind to the Child Component with the ngModel Syntax

[(name)]="firstname"

V2. Just create one @Input and @Output property with the naming you prefer

@Input() age : string;
@Output() ageChanged = new EventEmitter<string>();

with V2 you have to create two attributes to get the two way databinding

[age]="alter" (ageChanged)="alter = $event"

Parent Component

import { Component } from '@angular/core';

@Component({
   selector: 'my-app',
   template: `<p>V1 Parentvalue Name: "{{firstname}}"<br/><input [(ngModel)]="firstname" > <br/><br/>
              V2 Parentvalue Age: "{{alter}}" <br/><input [(ngModel)]="alter"> <br/><br/>

              <my-child [(name)]="firstname" [age]="alter" (ageChanged)="alter = $event"></my-child></p>`
})
export class AppComponent { 
    firstname = 'Angular'; 
    alter = "18"; 
}

Child Component

import { Component, Input, Output, EventEmitter } from '@angular/core';

@Component({
   selector: 'my-child',
   template: `<p>V1 Childvalue Name: "{{name}}"<br/><input [(ngModel)]="name" (keyup)="onNameChanged()"> <br/><br/>
              <p>V2 Childvalue Age: "{{age}}"<br/><input [(ngModel)]="age"  (keyup)="onAgeChanged()"> <br/></p>`
 })
export class ChildComponent { 
     @Input() name : string;
     @Output() nameChange = new EventEmitter<string>();

     @Input() age : string;
     @Output() ageChanged = new EventEmitter<string>();

     public onNameChanged() {
         this.nameChange.emit(this.name);
     }

     public onAgeChanged() {
         this.ageChanged.emit(this.age);
     }
 }