title: how to remove an object only if it exists on iPhone SDK?
body: <p>I want to remove a UILabel from the UIView dynamically. There are some branching and looping, and in the end when I remove it by 'removeFromSuperview' sdk crashes as it doesn't exist anymore, in some cases.</p>
  
  <pre><code>[lbl_timer removeFromSuperview];
  </code></pre>
  
  <p>So what i wanted is simply how to know if an object exists?</p>
  
  <p>thanks</p>