title: clearing a UITextField when the user starts typing
body: <p><strong>short version</strong>: How can I make a UITextField box remove all content on the users first keypress? I don't want the info removed until the user starts typing something. ie, clearing it on begin edit is not good enough.</p>
  
  <p><strong>long version</strong>: I have three UITextField that loop around (using the return key and catching the press in the "shouldReturn" method. There is text already in the UITextField, and if the user doesn't type anything and just goes to the next UITextField, the value should stay (default behaviour).</p>
  
  <p>But I want it that if the user starts typing, it automatically clears the text first. Something like having the whole field highlighted, and then typing anything deletes the fiels and then adds the user keypress. </p>
  
  <p>"Clear when editing begins" is no good, because the text is immediately cleared on the cursor appearing in the field. That's not desired. I thought I could use the placeholder here, but that doesn't work as a default, and I can't find a default value property. The Highlighted and Selected properties don't do anything in this regard either. </p>