OBJECTIVE-C (category classification, informal agreement, classification extension)

Classification:

The main is to add some methods to the original class; You cannot add member variables

Person (person+eat)

Informal agreements:

The informal agreement is the category, that is, the category that is added to the class in the framework of NSObject or its sub-class foundation, is an unjust agreement

Write a category to NSObject, NSObject class name (EAT), NSObject subclasses can inherit the method inside

Classification (category) extension

Extended categories are also called Extensions of classes:

@interface person Category (empty)//class extension

{

You can add properties

int _age;

}

Expansion methods

-(void) eat; A relative private method

@end

cannot be implemented in @implementation person () @end

Implemented directly in the @implementation person @end

OBJECTIVE-C (category classification, informal agreement, classification extension)