iOS关联对象

关联对象API

• 添加关联对象

void objc_setAssociatedObject(id _Nonnull object, const void * _Nonnull key,
                         id _Nullable value, objc_AssociationPolicy policy)

• 获得关联对象

id _Nullable objc_getAssociatedObject(id _Nonnull object,
									 const void * _Nonnull key)

• 移除所有的关联对象

void objc_removeAssociatedObjects(id _Nonnull object)

关联的引用

typedef OBJC_ENUM(uintptr_t, objc_AssociationPolicy) {
    OBJC_ASSOCIATION_ASSIGN = 0,          
    OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1,
    OBJC_ASSOCIATION_COPY_NONATOMIC = 3,  
    OBJC_ASSOCIATION_RETAIN = 01401,       
    OBJC_ASSOCIATION_COPY = 01403         
};

key的用法

1

- (void)setName:(NSString *)name
{
    objc_setAssociatedObject(self, @"name", name, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (NSString *)name
{
    return objc_getAssociatedObject(self, @"name")
}

2

static const char CMJNameKey;
- (void)setName:(NSString *)name
{
    objc_setAssociatedObject(self, &CMJNameKey, name, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (NSString *)name
{
    return objc_getAssociatedObject(self, &CMJNameKey)
}

3

 - (void)setName:(NSString *)name
{
    objc_setAssociatedObject(self, @selector(name), name, OBJC_ASSOCIATION_COPY_NONATOMIC);
}

 - (NSString *)name
{
    return objc_getAssociatedObject(self, @selector(name));
}

关联对象的原理

实现关联对象技术的核心对象有

• AssociationsManager
• AssociationsHashMap
• ObjectAssociationMap
• ObjcAssociation