title: How to wait for a closure completion before returning a value
body: <p>How to wait to return a value after a closure completion.</p>
  
  <p>Example:</p>
  
  <pre><code>func testmethod() -&gt; String {
     var abc = ""
     /* some asynchronous service call block that sets abc to some other value */ {
        abc = "xyz"
     }
     return abc 
  }
  </code></pre>
  
  <p>Now I want the method to return only after <code>xyz</code> value has been set for variable and not empty string. </p>
  
  <p>How to achieve this?</p>