Runtime 属性关联方法

通常情况下，我们用【类别】去对【原有类】进行【属性】的添加，如果在编译的时候不会报错，但是在运行阶段则会崩溃！
所以，我们通过对属性的set、get 方法重写并调用【关联属性】的方法，即可完成属性的 【赋值 和 打印】，并且不会崩溃。

static const char delegateKey //这是用来确认唯一身份的标识

■ 设置类关联属性 objc_setAssociatedObject (object , key , value , policy)

■ 获取类关联属性objc_getAssociatedObject (object , key)

object：被关联的对象（那个对象需要关联）
key：map表里key的一个唯一区分标志
value：属性
policy：属性以什么方式去保存（copy、strong、assign、retain等）

image.png

---

student.h

#import 

@interface CFStudent : NSObject
@property(nonatomic,copy)NSString *name;

//吃东西
- (void)eating;
@end

---

student.m

#import "CFStudent.h"
#import "CFStudent+Extension.h"
/*
 *扩展（私有：变量、属性）
 */
@interface CFStudent()
{
    NSInteger _num;     //学号
}
@property(nonatomic,assign)BOOL sex;
@end
@implementation CFStudent
//吃东西
- (void)eating
{
    _num = 123456;
    self.sex = YES;
    _class = @(2018);
    NSLog(@"_num:%ld   self.sex:%d   _class:%@",(long)_num,self.sex,_class);
    NSLog(@"Person eating！");
}


@end

---

CFStudent+Category.h

#import "CFStudent.h"
@protocol ExaminationRul
@optional
- (void)level6test;
@end

/*
 *分类（实例属性、类属性、实例方法、类方法、）
 */
@interface CFStudent (Category)
//注意：这些属性都使用不了，因为分类不能生成变量（内存已分配好），所以也没有setter、getter方法
@property(nonatomic,copy)NSString *age;
@property(class,nonatomic,copy)NSString *teacher;   //类属性使多个实例可以共享变量
@property(nonatomic,weak)id  delegate;

//玩耍
- (void)playing;
//睡觉
+ (void)sleeping;
@end

---

CFStudent+Category.m

#import "CFStudent+Category.h"
#import 
@implementation CFStudent (Category)
static const char ageKey;
static const char teacherKey;
static const char delegateKey;

- (void)setAge:(NSString *)age
{
    objc_setAssociatedObject(self, &ageKey, age, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (NSString *)age
{
    NSString *age = objc_getAssociatedObject(self, &ageKey);
    return age;
}

+ (void)setTeacher:(NSString *)teacher
{
    objc_setAssociatedObject(self, &teacherKey, teacher, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

+ (NSString *)teacher
{
    //注意：这里的self是CFStudent
    //而实例方法里的self是student
    NSString *teacher = objc_getAssociatedObject(self, &teacherKey);
    return teacher;
}

- (void)setDelegate:(id)delegate
{
    objc_setAssociatedObject(self, &delegateKey, delegate, 0);
}

- (id)delegate
{
    id delegate = objc_getAssociatedObject(self, &delegateKey);
    return delegate;
}

//玩耍
- (void)playing
{
    NSLog(@"Student playing！");
}
//睡觉
+ (void)sleeping
{
    NSLog(@"Student sleeping！");
}
- (void)level6test{
    NSLog(@"ExaminationRul-level6test！");
}
@end

---

CFStudent+Extension.h

#import "CFStudent.h"

@interface CFStudent ()
{
    NSNumber *_class;   //班级
}
@end

---

.main

#import 
#import "CFStudent.h"
#import "CFStudent+Category.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        CFStudent *student = [[CFStudent alloc]init];
        /*
         *1.属性
         */
        student.name = @"lilei";
        NSLog(@"student.name：%@",student.name);
        student.age = @"20";
        NSLog(@"student.age：%@",student.age);
        CFStudent.teacher = @"zhangsan";
        NSLog(@"CFStudent：%@",CFStudent.teacher);
        
        /*
         *2.方法
         */
        [student eating];
        [student playing];
        [CFStudent sleeping];
        
        /*
         *3.协议
         */
        student.delegate = student;
        [student.delegate level6test];
    }
    return 0;
}

---

打印结果:

2019-03-13 14:10:13.458535+0800 Category Associat的介绍[13462:1406592] student.name：lilei
2019-03-13 14:10:13.458766+0800 Category Associat的介绍[13462:1406592] student.age：20
2019-03-13 14:10:13.458803+0800 Category Associat的介绍[13462:1406592] wdwname:sdf
2019-03-13 14:10:13.458864+0800 Category Associat的介绍[13462:1406592] CFStudent：zhangsan
2019-03-13 14:10:13.458917+0800 Category Associat的介绍[13462:1406592] _num:123456   self.sex:1   _class:2018
2019-03-13 14:10:13.458945+0800 Category Associat的介绍[13462:1406592] Person eating！
2019-03-13 14:10:13.458961+0800 Category Associat的介绍[13462:1406592] Student playing！
2019-03-13 14:10:13.458979+0800 Category Associat的介绍[13462:1406592] Student sleeping！
2019-03-13 14:10:13.458998+0800 Category Associat的介绍[13462:1406592] ExaminationRul-level6test！
Program ended with exit code: 0