title: What language level support (if any) does Swift have for asynchronous programming?
body: <p>Asynchronous programming is a must for responsive user interfaces when application have to communicate over unpredictable networks (e.g.  smart phone applications).   The user interface must remain responsive while waiting for results to come back from servers somewhere over the internet.</p>
  
  <p>In most languages, the application programmer has to implement their own state machines (maybe using closures) to respond to asynchronous callbacks and/or coordinate multiply threads using locks.   </p>
  
  <p>Both of these are very error prone and not for the fait hearted! </p>
  
  <p>(c#  introduced the async keyword to help with this, <strong>only time (at least 5 years) will tell if it is a good solution</strong>.)</p>
  
  <p>Does Swift have any built in support to assist the writing of asynchronous code?</p>