title: how to achieve two way binding using ReactiveCocoa 4.0 and MVVM
body: <p>I am working in a project using Reactive Cocoa 4.0 and MVVM(swift 2.0).In view model I have string that will update according to the textfield changes,but i need to update that textfield if the string changes.Is it possible for two way binding between textfield and string(ageString).  </p>
  
  <pre><code>txtAge.rac_textSignal() ~&gt; RAC(objViewModel, "ageString")
  </code></pre>