title: What is an Objective-C "class continuation"?
body: <p>I can't quite figure out what I have seen <em>referred to as</em> an Objective-C <strong>"class continuation"</strong>.  Is this / are these…</p>
  
  <ol>
  <li>Ivar(s) declared in the <code>@implementation</code> (<code>.m</code>) file?</li>
  <li>Another name for a class category? (Unlikely, <em>ASFAIK</em> categories cannot have Ivars, period)</li>
  <li>Another name for a class extension?</li>
  <li>Something else?</li>
  </ol>
  
  <p><em>That said...</em></p>
  
  <ol>
  <li>What is the scope, lifetime, and usage case for such a thing?</li>
  <li>Is this an ARC-specific "feature"?</li>
  <li>Are there specific runtime, or other requirements for their use?</li>
  <li>Is this an appropriate place to create an <code>@property</code>, as well? And why would this be a better place for setting ivars or properties than, say, the <code>@interface</code> file / declaration?</li>
  <li>Why do people complicate discussions by using such specific terminology - that seems NOT to exist in any official documentation (that I could find)?</li>
  </ol>
  
  <p>In question <a href="https://stackoverflow.com/questions/9042480/in-objective-c-what-is-the-difference-between-defining-something-say-a-property">In Objective-C what is the difference between defining something (say a property) in the header file as opposed to the .m file?</a>
  the discussion touches on this issue, but sort of just clouds the issue further - or at least fails to provide a canonical reference / definition of the term… hence this question.</p>