1. 方法
- 通过一个key和协议关联对象和值
func objc_setAssociatedObject(_ object: Any, _ key: UnsafeRawPointer, _ value: Any?, _ policy: objc_AssociationPolicy)
- 通过对象和key获取关联
func objc_getAssociatedObject(_ object: Any, _ key: UnsafeRawPointer) -> Any?
- 移除所有关联
func objc_removeAssociatedObjects(_ object: Any)
2. objc_AssociationPolicy类型
一个弱引用给对象,类似assign标签
自动复制关联,类似copy标签
case OBJC_ASSOCIATION_COPY_NONATOMIC
关联对象为copy标签,但是关联过程不是原子的,相当于@property(copy, nonatomic)
自动关联对象为strong标签
case OBJC_ASSOCIATION_RETAIN_NONATOMIC
关联对象为strong标签,但是关联过程不是原子的,相当于@property(strong, nonatomic)
例子
#import <objc/runtime.h>
static void *EOCMyAlertViewKey = "EOCMyAlertViewKey";//自定义key值
- (void)askUserAQuestion {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Question"
message:@"What do you want to do?"
delegate:self
cancelButtonTitle:@"Cancel"
otherButtonTitles:@"Continue", nil];
void (^block)(NSInteger) = ^(NSInteger buttonIndex) {
if (buttonIndex == 0) {
[self doCancel];
} else {
[self doContinue];
}
};
objc_setAssociatedObject(alert, EOCMyAlertViewKey, block, OBJC_ASSOCIATION_COPY);//使用copy,把block从栈复制到堆里,保证本程序块结束block可用。
[alert show];
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
void (^block)(NSInteger) = objc_getAssociatedObject(alertView, EOCMyAlertViewKey);
block(buttonIndex);
}
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