这个可以解决变量传递问题, 就不用定义全局的了.
使用例子：
首先导入头文件：#import <objc/runtime.h>
设置静态常量：static char alertinfokey;
- (IBAction)showAlertAction:(id)sender {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"title" message:@"warn" delegate:selfcancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil];
objc_setAssociatedObject(alert, &alertinfokey, @"test value", OBJC_ASSOCIATION_RETAIN);
[alert show];
[alert release];
}
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
if (buttonIndex == 0) {
NSLog(@"== : %@",objc_getAssociatedObject(alertView, &alertinfokey));
}
}
输出结果：== : test value
ios扩展机制objc_setAssociatedObject，objc_getAssociatedObject,布布扣,bubuko.com
ios扩展机制objc_setAssociatedObject，objc_getAssociatedObject
原文：http://www.cnblogs.com/willbin/p/3673385.html