iOS的Runtime机制下给类别（category）添加属性、替换原有类的方法执行

OBJC_EXPORT void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)
    OBJC_AVAILABLE(10.6, 3.1, 9.0, 1.0);//set方法

OBJC_EXPORT id objc_getAssociatedObject(id object, const void *key)
    OBJC_AVAILABLE(10.6, 3.1, 9.0, 1.0);//get方法

OBJC_EXPORT void objc_removeAssociatedObjects(id object)
    OBJC_AVAILABLE(10.6, 3.1, 9.0, 1.0);//移除

- (void)setName:(NSString *)name{
    
//    OBJC_ASSOCIATION_ASSIGN = 0,           //assign
//    OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1, //retaion , nonatomic
//    OBJC_ASSOCIATION_COPY_NONATOMIC = 3,   //copy ,  nonatomic
//    OBJC_ASSOCIATION_RETAIN = 01401,       //retain
//    OBJC_ASSOCIATION_COPY = 01403          //copy
   /**
    实现set方法

    @param object#> self description#>
    @param key#> 属性的键值统一就行 description#>
    @param value#> 属性的值 description#>
    @param policy#> 和copy，retain，assign类似 description#>
    */
    objc_setAssociatedObject(self, nameKey, name, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

//定义常量 属性的键值统一
static char  *nameKey = "nameKey";

- (NSString *)name{
    /**
     实现get方法

     @param object#> 这是填self description#>
     @param key#> 属性的键值统一就行 description#>
     */
    return objc_getAssociatedObject(self, nameKey);

    SEL originalSelector = NSSelectorFromString(@"原来方法名");
    SEL swizzledSelector = NSSelectorFromString(@"需要替换的方法名");
    Method originalMethod = class_getInstanceMethod([self class], originalSelector);
    Method swizzledMethod = class_getInstanceMethod([self class], swizzledSelector);
    method_exchangeImplementations(originalMethod, swizzledMethod);