title: Removing multiple spaces in NSString
body: <p>I have a <code>NSString</code>, this has multiple spaces, I want to trim those spaces and make a single space for e.g.@"how.....are.......you" into @"how are you".(dots are simply spaces)</p>
  
  <p>I have tried with</p>
  
  <pre><code>NSString *trimmedString = [user_ids stringByTrimmingCharactersInSet:
                             [NSCharacterSet whitespaceCharacterSet]];
  </code></pre>
  
  <p>It not seems to work. Any idea.</p>