title: iOS equivalent of Android's Handler message queue
body: <p>Is there a standard way to build a message loop in iOS similar to Android's <a href="http://developer.android.com/reference/android/os/Handler.html" rel="nofollow">Handler</a> where I can send simple integer messages to a handler on a background thread? I want the main thread to do as little work as possible. I want to avoid even creating an Objective-C block on the main thread to send to a dispatch queue as the blocks to be run are quite big.</p>