title: iOS - Best practice for handling network response cross ViewControllers
body: <p>For example,
  There are 3 sequencial view controllers, A, B, C, in the navigation stack.
  After sending an async network request in view controller C in the background thread,
  User may go back to B or A.</p>
  
  <p>What is the best way to handle the network response no matter where the current view controller is?</p>
  
  <p>Thanks.</p>