title: Objective C @property in .h file vs @property in .m file
body: <p>In iOs Page based application template there is 2 different ways used to declare instance variable :</p>
  
  <p>one is declared in .h (DataViewController.h) as :</p>
  
  <pre><code>@interface DataViewController : UIViewController
  @property (strong, nonatomic) id dataObject;
  </code></pre>
  
  <p>the other is defined in .m as : </p>
  
  <pre><code>@interface ModelController()
  @property (readonly, strong, nonatomic) NSArray *pageData;
  @end
  </code></pre>
  
  <p>Is there any difference / advantage or is it just some old vs some new syntax ?</p>