title: How to debug "Collection was mutated while being enumerated" errors and like, when Xcode does not provide me with enough information?
body: <p>Currently, I see a recurring error:</p>
  
  <pre><code>2013-04-18 02:35:51.583 aaah[1713:1110f] *** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection &lt;__NSArrayM: 0x1fc00dc0&gt; was mutated while being enumerated.'
  </code></pre>
  
  <p>In the failing background queue (I see my queues state upon the moment of a crash by pressing Command + 5) I see:</p>
  
  <pre><code>0 _pthread_kill
  1 pthread_kill
  </code></pre>
  
  <p>And I see assembly output which I completely don't understand.</p>
  
  <p>I know how to resolve this kind of array enumeration errors - I just can't understand where/how I should seek for the piece of code causing my app to crash.</p>
  
  <p>I have much multi-threaded code using AFNetworking and Core Data, so I can't just remember where the crucial section might be.</p>
  
  <p>Also, this error occurs not always, but from time to time, so it is difficult just to use "isolation approach", isolating smaller and smaller pieces of code, to finally identify the buggy piece of code. </p>
  
  <p>So the question is:</p>
  
  <p><strong>How can I extract some more useful information from this output, or Xcode can provide me with some more verbosity level, so I could know how to resolve this annoying piece of code.</strong></p>