Objective-C Runtime之着魔的UIAlertView

原文出处： ian博客（@ianisme ）

传统的UIAlertView：

在一个类中有多个UIAlertView，不同的UIAlertView对应不同的事件，我们使用的传统方法如下：

Objective-C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

#pragma mark - action method - (IBAction)firstButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.tag = 1001; [alertView show]; } - (IBAction)secondButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.tag = 1002; [alertView show]; } - (IBAction)ThirdButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.tag = 1003; [alertView show]; } #pragma mark - delegate method - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (alertView.tag == 1001) { if (buttonIndex == 1) { NSLog(@"普通alertView1001执行ok"); } } else if (alertView.tag == 1002) { if (buttonIndex == 1) { NSLog(@"普通alertView1002执行ok"); } } else if (alertView.tag == 1003) { if (buttonIndex == 1) { NSLog(@"普通alertView1003执行ok"); } } }

我们要给每个UIAlertView赋值一个tag值，在delegate方法中还要进行tag的判断以及buttonIndex的判断，太繁琐了。

着魔的UIAlertView：

下面我们使用Category和Associated Objects进行魔法修改

创建一个UIAlertView的Category

UIAlertView+ActionBlock.h

Objective-C

1 2 3 4 5 6 7 8 9

#import <UIKit/UIKit.h> typedef void (^AlertCallBack)(UIAlertView *, NSUInteger); @interface UIAlertView (ActionBlock)<UIAlertViewDelegate> @property (nonatomic, copy) AlertCallBack callBack; @end

UIAlertView+ActionBlock.m

Objective-C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

#if TARGET_IPHONE_SIMULATOR #import <objc/objc-runtime.h> #else #import <objc/runtime.h> #import <objc/message.h> #endif @implementation UIAlertView (ActionBlock) - (void)setCallBack:(AlertCallBack)callBack { objc_setAssociatedObject(self, @selector(callBack), callBack, OBJC_ASSOCIATION_COPY_NONATOMIC); self.delegate = self; } - (AlertCallBack)callBack { return objc_getAssociatedObject(self, @selector(callBack)); } #pragma mark - delegate method - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (self.callBack) { self.callBack(alertView, buttonIndex); } }

在主类中取消delegate，使用block属性

Objective-C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

#pragma mark - action method - (IBAction)firstButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.callBack = ^(UIAlertView *alertView, NSUInteger buttonIndex){ if (buttonIndex == 1) { NSLog(@"魔法alertView1001执行ok"); } }; [alertView show]; } - (IBAction)secondButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.callBack = ^(UIAlertView *alertView, NSUInteger buttonIndex){ if (buttonIndex == 1) { NSLog(@"魔法alertView1002执行ok"); } }; [alertView show]; } - (IBAction)ThirdButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.callBack = ^(UIAlertView *alertView, NSUInteger buttonIndex){ if (buttonIndex == 1) { NSLog(@"魔法alertView1003执行ok"); } }; [alertView show]; }

我们通过使用Category给UIAlertView扩展了一个block属性，当block被设置后就会调用setCallBack方法，触发self.delegate = self，即主类中的UIAlertView的delegate方法被Category中的方法覆盖。这样不仅有效解决问题，还解决了其他人修改该类的安全性（block被去掉后，原delegate恢复）

如下不给tag值为1003的UIAlertView设置block，即调用原delegate方法。

Objective-C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61

- (IBAction)firstButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.callBack = ^(UIAlertView *alertView, NSUInteger buttonIndex){ if (buttonIndex == 1) { NSLog(@"魔法alertView1001执行ok"); } }; alertView.tag = 1001; [alertView show]; } - (IBAction)secondButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.callBack = ^(UIAlertView *alertView, NSUInteger buttonIndex){ if (buttonIndex == 1) { NSLog(@"魔法alertView1002执行ok"); } }; alertView.tag = 1002; [alertView show]; } - (IBAction)ThirdButtonClick:(id)sender { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"ok", nil]; alertView.tag = 1003; [alertView show]; } - (IBAction)fourthButtonClick:(id)sender { UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"title" message:@"message" preferredStyle:UIAlertControllerStyleAlert]; UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"cancel" style:UIAlertActionStyleCancel handler:nil]; UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction *alertAction){ NSLog(@"如果你是iOS8以上的应用，这个适合你，简单明了"); }]; [alertController addAction:cancelAction]; [alertController addAction:okAction]; [self presentViewController:alertController animated:YES completion:nil]; } #pragma mark - delegate method - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (alertView.tag == 1001) { if (buttonIndex == 1) { NSLog(@"普通alertView1001执行ok"); } } else if (alertView.tag == 1002) { if (buttonIndex == 1) { NSLog(@"普通alertView1002执行ok"); } } else if (alertView.tag == 1003) { if (buttonIndex == 1) { NSLog(@"普通alertView1003执行ok"); } } else if (alertView.tag == 1004) { if (buttonIndex == 1) { NSLog(@"普通alertView1004执行ok"); } } }

相关Demo下载：

https://github.com/ianisme/UIAlertViewBYRuntime_Demo

总结：

通过Associated Objects我们有效的解决了UIAlertView的繁琐问题，如果您是开发iOS8以上的应用，建议您弃用UIAlertView，苹果的UIAlertController已经有了更好的解决方案。QQ技术交流群290551701