When to Use Subclassing in iPad App Development

Subclassing is one of the mechanisms you use to customize behaviors while you're developing your iPad application. Subclassing involves two stages: (1) creating a new class, called a subclass, that inherits properties from another (super) class and then (2) adding properties as needed for your iPad application. In general, you’ll want to subclass

• UIView, to create your (more complex) content views, which you may fill with controls, graphics, or the like.

  
  



• UIViewController, to manage the content views and connect it to the model.

  
  



• NSObject, to create Model views and delegates.

  
  

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Source:http://www.dummies.com/how-to/content/when-to-use-subclassing-in-ipad-app-development.html