title: Is NSUserDefault thread safe?
body: <p><a href="https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html">https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html</a> says it is</p>
  
  <blockquote>
    <p>...should prevent users from editing that preference by disabling any
    appropriate controls.</p>
    
    <p>The <strong>NSUserDefaults class is thread-safe.</strong> Persistence of NSURL and
    file reference URLs...</p>
  </blockquote>
  
  <p>This long discussion says it isn't</p>
  
  <p><a href="http://www.cocoabuilder.com/archive/cocoa/155227-nsuserdefaults-thread-safety.html">http://www.cocoabuilder.com/archive/cocoa/155227-nsuserdefaults-thread-safety.html</a></p>
  
  <p>So which one is right? Also why the difference of opinion.</p>