title: convert string to number angular 2 one way binding
body: <p>convert the string to number angular 2 one way binding</p>
  
  <pre><code>[longitude]="loc.location.lng"&gt;
  </code></pre>
  
  <p>loc.location.lng is string i need to convert them to number.but still not working as I expect.
  In interpolation it's working but in this not working.
  Thanks</p>