title: What is the correct way to fetch data from remote server periodically in iOS when app is background?
body: <p>I need to fetch data from server and (probably) create local notifications for user.
  When in foreground, I use separate queue. I can do that when I am in background (after Home button clicked) as well, but there is also "background fetch" feature.</p>
  
  <p>Which one should I use? Is it better to simply use queue or background thread and leave it when app goes to background, or should I pause my thread and wait for "background fetch" request?</p>