title: Angular 2 two way data binding not working
body: <p>I'm having trouble getting custom two way data binding to work in Angular 2. The Docs indicate that the banana in a box model - [()] is just syntatic sugar, however in my example this way doesn't work and the longer method works:  </p>
  
  <pre><code>&lt;child-component [(test)]="check"&gt;This child updates only itself&lt;/child-component&gt;
  &lt;child-component [test]="check" (check_send)="check=$event"&gt;This child updates all&lt;/child-component&gt;
  </code></pre>
  
  <p>The @Output event is not changing the parent value in the banana in a box model (first line).
    As the second line works I don't see what I am doing wrong.
    Here is a link to the docs: <a href="https://angular.io/guide/template-syntax#two-way-binding---" rel="nofollow noreferrer">https://angular.io/guide/template-syntax#two-way-binding---</a></p>
  
  <p>Here is a plunker I have created to showcase this behavior:<a href="https://embed.plnkr.co/eTfkQmRfBRxeKCEpGdzh/" rel="nofollow noreferrer">https://embed.plnkr.co/eTfkQmRfBRxeKCEpGdzh/</a></p>
  
  <p>Edit: This is a different question to a possible duplicate because this question does not produce any errors, plus it is a much more simple and localised problem with the formatting of two way bind.</p>