ios runtime 动态属性objc_setAssociatedObject和objc_getAssociatedObject

//
// ViewController.m
// objc_runtime
//
// Created by 王飞 on 16/4/11.
// Copyright © 2016年 com.startchina. All rights reserved.
//

#import "ViewController.h"
#import <objc/runtime.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    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。
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end