Objective-C Runtime之着魔的UIAlertView

原文出處： ian博客（@ianisme ）   

傳統的UIAlertView：

在一個類中有多個UIAlertView，不一樣的UIAlertView對應不一樣的事件，咱們使用的傳統方法以下：

Objective-C

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#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執行ok");         }     } else if (alertView.tag == 1002) {         if (buttonIndex == 1) {             NSLog(@"普通alertView1002執行ok");         }     } else if (alertView.tag == 1003) {         if (buttonIndex == 1) {             NSLog(@"普通alertView1003執行ok");         }     } }

咱們要給每一個UIAlertView賦值一個tag值，在delegate方法中還要進行tag的判斷以及buttonIndex的判斷，太繁瑣了。

着魔的UIAlertView：

下面咱們使用Category和Associated Objects進行魔法修改

建立一個UIAlertView的Category

UIAlertView+ActionBlock.h

Objective-C

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

UIAlertView+ActionBlock.m

Objective-C

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#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);     } }

在主類中取消delegate，使用block屬性

Objective-C

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#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執行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執行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執行ok");         }     };     [alertView show]; }

咱們經過使用Category給UIAlertView擴展了一個block屬性，當block被設置後就會調用setCallBack方法，觸發self.delegate = self，即主類中的UIAlertView的delegate方法被Category中的方法覆蓋。這樣不只有效解決問題，還解決了其餘人修改該類的安全性（block被去掉後，原delegate恢復）

以下不給tag值爲1003的UIAlertView設置block，即調用原delegate方法。

Objective-C

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- (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執行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執行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以上的應用，這個適合你，簡單明瞭");     }];     [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執行ok");         }     } else if (alertView.tag == 1002) {         if (buttonIndex == 1) {             NSLog(@"普通alertView1002執行ok");         }     } else if (alertView.tag == 1003) {         if (buttonIndex == 1) {             NSLog(@"普通alertView1003執行ok");         }     } else if (alertView.tag == 1004) {         if (buttonIndex == 1) {             NSLog(@"普通alertView1004執行ok");         }     } }

相關Demo下載：

https://github.com/ianisme/UIAlertViewBYRuntime_Demo

總結：

經過Associated Objects咱們有效的解決了UIAlertView的繁瑣問題，若是您是開發iOS8以上的應用，建議您棄用UIAlertView，蘋果的UIAlertController已經有了更好的解決方案。QQ技術交流羣290551701