协议与分类--24：分类（Category）

xy_ss

发布于 2023-11-22 08:24:36

1910

发布于 2023-11-22 08:24:36

文章被收录于专栏：浮躁的喧嚣

分类

Category也称为分类、类目、类别等，Category可以在不修改原来类的基础上，为这个类补充一些方法

Category的格式

@interface Person (SS)
    -(void)eat;
@end

Category的运用

在开发中，类的实现文件特别大，难于管理与维护，因此经常使用分类机制把类的实现代码划分成易于管理的小块，以便单独检视

#import <Foundation/Foundation.h>
@interface Person : NSObject
@property (nonatomic,copy) NSString *firstName;
@property (nonatomic,copy) NSString *lastName;
@property (nonatomic,strong) NSArray *friendArray;

- (instancetype)initWithFristName:(NSString *)firstName withLastName:(NSString *)lastName;
- (void)addPerson:(Person *)person;
- (void)removePerson:(Person *)person;
- (BOOL)isFriendWithPerson:(Person *)person;
- (void)performDayWork;
- (void)takeVacationFromWork;
- (void)gotoTheCinema;
- (void)gotoSportGame;
@end

实现文件里，所有的方法都写在一个类，内容太多，所以我们可根据其不同功能分成多个分类

#import <Foundation/Foundation.h>
@interface Person : NSObject
@property (nonatomic,copy) NSString *firstName;
@property (nonatomic,copy) NSString *lastName;
@property (nonatomic,strong) NSArray *friends;
- (instancetype)initWithFristName:(NSString *)firstName withLastName:(NSString *)lastName;
@end
-------------------------
#import "Person.h"
@interface Person (Work)
- (void)performDayWork;
- (void)takeVacationFromWork;
@end
-------------------------
#import "Person.h"
@interface Person (Play)
- (void)gotoTheCinema;
- (void)gotoSportGame;
@end
-------------------------
#import "Person.h"
@interface Person (Friendship)
- (void)addPerson:(Person *)person;
- (void)removePerson:(Person *)person;
- (BOOL)isFriendWithPerson:(Person *)person;
@end

如果分类中有和原类中同名的方法，程序只会调用分类里的方法，如果多个分类中都有和原类中同名的方法，程序只会由编译器决定，编译器最后一个执行的方法来响应

@interface Person : NSObject
@property (nonatomic,strong) NSString *name;
-(void)sayName;
@end
@implementation Person
-(void)sayName{
    NSLog(@"%@",self.name);
}
@end
------------------------------------
@interface Person (SS)
-(void)eat;
-(void)sayName;
@end
@implementation Person (SS)
-(void)eat{
    NSLog(@"%s",__func__);
}
-(void)sayName{
    NSLog(@"%s",__func__);
}
@end
-------------------------------------
int main(int argc, const char * argv[]) {
    Person *p = [[Person alloc]init];
    p.name = @"ABC";
    [p sayName];
    [p eat];
}