title: Check for Reachability in viewDidAppear or AppDelegate?
body: <p>I am using AlamoreFire and checking for network reachability in two of the app's view controllers in the viewDidAppear method of both. But sometimes when the network is found the view controller collection view loads twice.
  I am guessing that maybe the Reachability should be put in one place only in the entire app.</p>
  
  <p>What is the best and cleanest way to implement Reachability when you have multiple view controllers to check?
  I would like to use the NetworkReachabilityManager from AlamoFire.</p>