iOS 5 Programming Cookbook

1.16. Adding Properties to Classes

Problem

You want to add properties to your classes so that you can take advantage of dot notation to access those values, as opposed to using methods on your classes.

Solution

Define properties in your classes using the @property keyword.

Discussion

Anything addressed via dot notation is a property. Properties are shortcuts to methods. What do I mean? Well, let’s have a look at an example:

NSObject *myObject = [[NSObject alloc] init];
myObject.accessibilityHint = @"Some string";

You can see that we allocated and initialized an object of type NSObject and used dot notation to access a property called accessibilityHint in that object. Where did accessibilityHint come from?

It’s quite simple. A property is defined using the @property keyword. In fact, if you hold down the Command key on your keyboard in Xcode, and simply click on the accessibilityHint property in the example that we just saw, you will be redirected to the NSObject.h file where you will see this:

@property(nonatomic, copy) NSString *accessibilityHint;

But what are properties? Well, when we define a property, we tell the compiler that we will write a setter and a getter method for this property. If somebody tries to set a value in this property, the runtime will execute our setter method. If somebody tries to read from the property, the runtime will execute the getter method.

Let’s see this in detail. In Recipe 1.12 we saw how we create classes. We created a class called Person. In Recipe 1.13 ...