title: What is the strong property attribute
body: <p>I am using the Xcode beta for developers, and am noticing some subtle differences. Among them is a new attribute for declared properties.</p>
  
  <pre><code>@property(strong)IBOutlet NSArrayController *arrayControl;
  </code></pre>
  
  <p>My question is: what does the strong attribute mean?? Does it replace some older one, or is it something entirely new? I have searched through google and the developer documentation and havent been able to find anything. Until i know what it is i am hesitant to use it.</p>
  
  <p>Thanks in advance</p>