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今天讲Objective-C的@property

Properties Control Access to an Object’s Values
Objects often have properties intended for public access. If you define a class to represent a human being in a record-keeping app, for example, you might decide you need properties for strings representing a person’s first and last names.
Declarations for these properties should be added inside the interface, like this:

@interface Person : NSObject @property NSString *firstName;@property NSString *lastName; @end

In this example, the Person class declares two public properties, both of which are instances of the NSString class.
Both these properties are for Objective-C objects, so they use an asterisk to indicate that they are C pointers. They are also statements just like any other variable declaration in C, and therefore require a semi-colon at the end.
You might decide to add a property to represent a person’s year of birth to allow you to sort people in year groups rather than just by name. You could use a property for a number object:

@property NSNumber *yearOfBirth;

but this might be considered overkill just to store a simple numeric value. One alternative would be to use one of the primitive types provided by C, which hold scalar values, such as an integer:

@property int yearOfBirth;