iOS-runtime-objc_setAssociatedObject（关联对象以及传值）

static const char kRePResentedObject;- (IBAction)doSomething:(id)sender {  UIAlertView *alert = [[UIAlertView alloc]                        initWithTitle:@"Alert" message:nil                        delegate:self                        cancelButtonTitle:@"OK"                        otherButtonTitles:nil];  objc_setAssociatedObject(alert, &kRepresentedObject,                            sender,                           OBJC_ASSOCIATION_RETAIN_NONATOMIC);  [alert show];  }- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {  UIButton *sender = objc_getAssociatedObject(alertView,                                               &kRepresentedObject);  self.buttonLabel.text = [[sender titleLabel] text];}