title: UITextField highlight text when user taps space
body: <p>I have a <code>UITextField</code> which i let user write tags as we do in stackoverflow. What i really want is exactly what stackoverflow does,with a slight difference which is to detect user's touch space button in keyboard.Well,stackoverflow searches instantaneously and display results.Instead i want user to tap space button. Do u guys have any idea,any tutorial that i can benefit from ? I'm sure i'm going to use UITextFieldDelegate method which is </p>
  
  <p><br><code>-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string</code><br> </p>
  
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  But i don't know  how to highlight the words before user starts to tap another word .</p>