title: KnockoutJS options binding, unable to set value in parent context
body: <pre><code>&lt;select data-bind='foreach: theOptions'&gt;
      &lt;option data-bind='text: name, value: $root.watchThis().something'&gt;&lt;/option&gt;
  &lt;/select&gt;
  You have selected &lt;p data-bind="text: watchThis().something"&gt;&lt;/p&gt;
  
  Json model.
  &lt;p data-bind="text: ko.toJSON(watchThis)"&gt;&lt;/p&gt;
  </code></pre>
  
  <p>Options are being shown, but when i change value the relative observable is not updated.
  More code:</p>
  
  <pre><code>function FooModel() {
      this.something = ko.observable();   
  }
  
  function VM() {
      var self = this;
      self.watchThis = ko.observable(new FooModel());
      self.theOptions = ko.observableArray();
  
      self.theOptions([
          {id:1, name: 'foo'},
          {id:2, name: 'bar'},
          {id:3, name: 'baz'}
      ]);
  }
  ko.applyBindings(new VM());
  </code></pre>
  
  <p>I also tried </p>
  
  <pre><code>&lt;option data-bind='text: name, value: $root.watchThis().something'&gt;&lt;/option&gt;
  &lt;option data-bind='text: name, value: $root.watchThis.something'&gt;&lt;/option&gt;
  &lt;option data-bind='text: name, value: $parent.watchThis().something'&gt;&lt;/option&gt;
  </code></pre>
  
  <p>What seems worst, if i explicitly initialize the value like this</p>
  
  <pre><code>function FooModel() {
      this.something = ko.observable(2);   
  }
  </code></pre>
  
  <p>everything looks fine, but when i switch options the observable is not updated.</p>
  
  <p><a href="http://jsfiddle.net/6gvdP/2" rel="nofollow">JSFiddle here</a></p>
  
  <p>Question is: how to update an observable from an external context using the option selected value?</p>