如何让自己的类具有copy修饰符,如何重写带copy关键字的se

若想令自己的类具有拷贝功能,则需实现NSCopying 协议,如果自定义的对象分为可变版本与不可变版本的话,那就要同时实现NSCopying与NSMutableCopying协议

具体步骤
1 声明该类遵从NSCopying协议
2.实现NSCopying 这个协议只有一个方法

    -(id)copyWithZone:(NSZone*)zone;

    - (instancetype)initWithName:(NSString *)name age:(NSUInteger)age sex:(CYLSex)sex;

这么实现的

    - (id)copyWithZone:(NSZone *)zone {
    CYLUser *copy = [[[self class] allocWithZone:zone] 
                     initWithName:_name
                                  age:_age
                                  sex:_sex];
    return copy;
}

     - (void)setName:(NSString *)name {
    if (_name != name) {
        //[_name release];//MRC
        _name = [name copy];
    }
}

那如何确保 name 被 copy？在初始化方法(initializer)中做：

    - (instancetype)initWithName:(NSString *)name 
                                 age:(NSUInteger)age 
                                 sex:(CYLSex)sex {
         if(self = [super init]) {
            _name = [name copy];
            _age = age;
            _sex = sex;
            _friends = [[NSMutableSet alloc] init];
         }
         return self;
    }