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，不一样的UIAlertView对应不一样的事件，咱们使用的传统方法以下：

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");         }     } }

咱们要给每一个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：

下面咱们使用Category和Associated Objects进行魔法修改

建立一个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]; }

咱们经过使用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。这样不只有效解决问题，还解决了其余人修改该类的安全性（block被去掉后，原delegate恢复）

以下不给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(@"若是你是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：

经过Associated Objects咱们有效的解决了UIAlertView的繁琐问题，若是您是开发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