Categories in Objective-C

Very elegant concept introduced by apple in objective-c programming language is 'Category'.
We can treat them to extending the functionality of existing class.

• Used to "Customise the existing class" i.e. to extend the functionalities of existing class.
• Category made for a class will also available for all its subsequent subclasses.
• Scope of category is to the entire application.
• We can name the Category as existing class name so no need to remember new name.
• Data variables are not available to use only Member functions.
• Very easy to create.

Resources:

• https://developer.apple.com/library/ios/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html
• http://mobile.tutsplus.com/tutorials/iphone/objective-c-categories/