iPhone开源系列：UIAlertView-Block

来源：互联网发布：ubuntu 命令行上下编辑：程序博客网时间：2024/05/19 04:27

UIAlertView和UIActionSheet都采用了Delegate模式，在同一个视图控制器中使用多个UIAlertView或UIActionSheet时控制器需要同时充当它们的delegate，这种情况下处理函数中通常需要通过tag进行区分后处理。这样就经常会造成如下代码：

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if ([alertView tag] == LOGIN_ERROR_ALERT) {    // it's alert for login error
        if (buttonIndex == 0) {     // and they clicked OK.
            // do stuff
        }
    }
    else if ([alertView tag] == UPDATE_ERROR_ALERT) {   // it's alert for update error
        if (buttonIndex == 0) {     // and they clicked OK.
            // do stuff
        }
    }
    else {
    }
}

这种针对tag的分支判断就会影响到代码可读性，并产生坏味道。UIAlertView-Block（https://github.com/jivadevoe/UIAlertView-Blocks）项目就可以克服这样的问题。该项目提供了可以使用代码块来处理按钮事件的UIAlertView和UIActionSheet的Category，示例代码如下：

RIButtonItem *cancelItem = [RIButtonItem item];
cancelItem.label = @"No";
cancelItem.action = ^
{
    // this is the code that will be executed when the user taps "No"
    // this is optional... if you leave the action as nil, it won't do anything
    // but here, I'm showing a block just to show that you can use one if you want to.
};

RIButtonItem *deleteItem = [RIButtonItem item];
deleteItem.label = @"Yes";
deleteItem.action = ^
{
    // this is the code that will be executed when the user taps "Yes"
    // delete the object in question...
    [context deleteObject:theObject];
};

UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Delete This Item?" message:@"Are you sure you want to delete this really important thing?" cancelButtonItem:cancelItem otherButtonItems:deleteItem, nil]; [alertView show]; [alertView release];

有了这样一个项目，是不是再次看到根据tag区分进行分支处理时会有一种重构的冲动呢？

本文出自 “林家男孩” 博客，请务必保留此出处http://bj007.blog.51cto.com/1701577/635845

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