比如说给UIView 添加一个name 的属性,
步骤:
1. 创建 UIView + addProperty.h / UIView + addProperty.m 的类目,
然后在UIView + addProperty.h 中添加一个属性,
@property(nonatomic,strong)NSString *name;
2. 在.m 中重写get /set 方法.
@dynamic name;
static char charKey;
- (void)setName:(NSString *)name
{
objc_setAssociatedObject(self, &charKey, name, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (NSString *)name
{
return objc_getAssociatedObject(self, &charKey);
}
3. 解释一下 objc_setAssociatedObject 方法
//1 源对象(在这里 是给view 添加的属性,所以 就是 view 自己)
//2 关键字 唯一静态变量key associatedkey
//3 关联的对象 ,这个地方是name值,sender
//4 关键策略 OBJC_ASSOCIATION_ASSIGN
// enum {
// OBJC_ASSOCIATION_ASSIGN = 0, 若引用/**< Specifies a weak reference to the associated object. */
// OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1, /**< Specifies a strong reference to the associated object.
// * The association is not made atomically. */
// OBJC_ASSOCIATION_COPY_NONATOMIC = 3, /**< Specifies that the associated object is copied.
// * The association is not made atomically. */
// OBJC_ASSOCIATION_RETAIN = 01401, /**< Specifies a strong reference to the associated object.
// * The association is made atomically. */
// OBJC_ASSOCIATION_COPY = 01403 /**< Specifies that the associated object is copied.
// * The association is made atomically. */
// };