有没有委托处理UIAlertView结果的简单方法？

Question

我有一个显示带有YES/NO按钮的UIAlertView的函数,它只在函数范围内使用,因此我不想实现委托以捕获用户反馈.

有没有办法知道用户点击的按钮没有实现UIAlertViewDelegate,如:

[alert show];
if([alert indexOfClickedButton] == indexOfYes)
{
....
}

或者像动画中的lambda表达式

Answer 1

没有办法完全避免委托,但你可以沿着这些方向创建一个包装器:

@interface MyAlertViewDelegate : NSObject<UIAlertViewDelegate>

typedef void (^AlertViewCompletionBlock)(NSInteger buttonIndex);
@property (strong,nonatomic) AlertViewCompletionBlock callback;

+ (void)showAlertView:(UIAlertView *)alertView withCallback:(AlertViewCompletionBlock)callback;

@end


@implementation MyAlertViewDelegate
@synthesize callback;

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    callback(buttonIndex);
}

+ (void)showAlertView:(UIAlertView *)alertView
         withCallback:(AlertViewCompletionBlock)callback {
    __block MyAlertViewDelegate *delegate = [[MyAlertViewDelegate alloc] init];
    alertView.delegate = delegate;
    delegate.callback = ^(NSInteger buttonIndex) {
        callback(buttonIndex);
        alertView.delegate = nil;
        delegate = nil;
    };
    [alertView show];
}

@end

(假设ARC,如果您不使用它,则更delegate = nil改为[delegate release].)

用法如下:

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Confirm" message:@"Yes or No?" delegate:nil cancelButtonTitle:@"Cancel" otherButtonTitles:@"Yes",@"No", nil];
[MyAlertViewDelegate showAlertView:alert withCallback:^(NSInteger buttonIndex) {
    // code to take action depending on the value of buttonIndex
}];