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：
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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");
}
}
}
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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
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#import <UIKit/UIKit.h>
typedef void (^AlertCallBack)(UIAlertView *, NSUInteger);
@interface UIAlertView (ActionBlock)<UIAlertViewDelegate>
@property (nonatomic, copy) AlertCallBack callBack;
@end
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UIAlertView+ActionBlock.m
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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);
}
}
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在主类中取消delegate，使用block属性
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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];
}
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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。
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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");
}
}
}
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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