Learning Objective-C 2.0: A Hands-on Guide to Objective-C for Mac and iOS Developers, Second Edition

12. Properties

One of the most common programming tasks is to set or retrieve a value held in one of an object’s instance variables. Although it is possible in some cases to access the instance variable directly, doing so is a bad practice. The correct way to access an instance variable is to write accessor methods. An accessor method that sets an instance variable’s value is called a setter, and one that returns an instance variable’s value is called a getter.

For example, if your object has the integer instance variable numberOfDogs, you should declare and implement the following two methods:

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     // returns the current value-(NSInteger) numberOfDogs;     //  sets a new value-(void)setNumberOfDogs:(NSInteger) newNumberOfDogs; ...