objc_setAssociatedObject 使用(转)

- (void)viewDidLoad {

[super viewDidLoad];

// static const char associatedButtonkey;

UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];

[btn setTitle:@"点我" forState:UIControlStateNormal];

[self.view addSubview:btn];

[btn setFrame:CGRectMake(50, 50, 50, 50)];

btn.backgroundColor = [UIColor redColor];

[btn addTarget:self action:@selector(click:) forControlEvents:UIControlEventTouchUpInside];

// Do any additional setup after loading the view, typically from a nib.

}

-(void)click:(UIButton *)sender

{

NSString *message = @"你是谁";

UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"提示" message:@"我要传值·" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];

alert.delegate = self;

[alert show];

//#import <objc/runtime.h>头文件

//objc_setAssociatedObject需要四个参数：源对象，关键字，关联的对象和一个关联策略。

//1 源对象alert

//2 关键字唯一静态变量key associatedkey

//3 关联的对象 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. */

// };

objc_setAssociatedObject(alert, @"msgstr", message,OBJC_ASSOCIATION_ASSIGN);

//把alert和message字符串关联起来，作为alertview的一部分，关键词就是msgstr，之后可以使用objc_getAssociatedObject从alertview中获取到所关联的对象，便可以访问message或者btn了

// 即实现了关联传值

objc_setAssociatedObject(alert, @"btn property",sender,OBJC_ASSOCIATION_ASSIGN);

}

-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex

{

//通过 objc_getAssociatedObject获取关联对象

NSString *messageString =objc_getAssociatedObject(alertView, @"msgstr");

UIButton *sender = objc_getAssociatedObject(alertView, @"btn property");

NSLog(@"%ld",buttonIndex);

NSLog(@"%@",messageString);

NSLog(@"%@",[[sender titleLabel] text]);

//使用函数objc_removeAssociatedObjects可以断开所有关联。通常情况下不建议使用这个函数，因为他会断开所有关联。只有在需要把对象恢复到“原始状态”的时候才会使用这个函数。

}

终端打印：

2015-07-22 16:18:35.294 test[5174:144121] 0

2015-07-22 16:18:35.295 test[5174:144121] 你是谁

2015-07-22 16:18:35.295 test[5174:144121] 点我

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