title: SAPUI5 Expression Binding
body: <p>Is it possible to bind control property to model with dynamic property name, stored, for instance, within another model field? I thought we can use SAPUI5 <a href="https://sapui5.hana.ondemand.com/docs/guide/daf6852a04b44d118963968a1239d2c0.html" rel="nofollow">Expression Binding</a> for this purpose, but it doesn't work: binding in trace window is broken and expression seems to be not evaluated at all.</p>
  
  <p><strong>XML View</strong></p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;TextArea value="{= ${StackOverflow&gt;/bindTextAreaTo} }" /&gt;
  </code></pre>
  
  <p><strong>Controller</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>oModel = this.getView().getModel("StackOverflow");
  
  /*
   * The model have two properties: question and comment
   * I want value of TextArea to be bound to one of them based on some condition
   */
  
  oModel.setProperty("/question", "");
  oModel.setProperty("/comment", "");
  
  oModel.setProperty("/bindTextAreaTo", 
      bAsk ? "StackOverflow&gt;/question" : "StackOverflow&gt;/comment" );
  </code></pre>