title: Serializing asynchronous methods
body: <p>I have a number of tasks I need to execute serially but the task includes next block in a completion block.</p>
  
  <p>What is a good technique for doing these tasks one at a time, starting the next task after the current one completes its completion block?</p>
  
  <p>Is there a technique other than a NSOperation subclass with a serial NSOperationQueue?</p>