title: Accessing NSManagedObject from background thread
body: <p>So I know <code>NSManagedObjects</code> are not thread safe, and the best way to get objects from a background thread is to use <code>[context objectWithId:id];</code> , and so pass around object ids instead of the actual object.</p>
  
  <p>Let's say I have a global <code>NSManagedObject</code> in my <code>AppDelegate</code> (not the best design pattern, but just for example) <code>NSManagedObject *myObject;</code></p>
  
  <p>Is it safe to access this object's <code>objectId</code> from a background thread? Like this:</p>
  
  <pre><code>dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
          objectId = appDelegate.myObject.objectId;
          //is this thread safe?
  }
  </code></pre>