UIAlertAction的处理程序不起作用

Question

我是新手，现在正在学习一本教程书。 这本书有点过时了，我有这个错误。

基本上，我试图进行表格单元格的选择，选择单元格后，它应该会弹出一个菜单，然后可以点击通话按钮。 但是，在我按下调用按钮后，现在没有出现预期的更改框，并且编译器给了我错误： 不允许尝试在取消分配时加载视图控制器的视图，这可能导致未定义行为

编辑代码时没有错误，只是无法正常运行。

另一个问题是我的桌子上大约有17行，刺激器的屏幕上仅显示7行，而我无法向下滚动以查看其余的行。

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath:NSIndexPath){

    //this creates an option menu when you tap on the row
    let optionMenu = UIAlertController(title: nil, message: "What do you want to do?", preferredStyle: .ActionSheet)
    //this is what happened after you hit the cancel option
    let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel, handler: nil)
    //defines the action after tap on the call option
    let nocallAction = UIAlertAction(title: "OK", style: .Default, handler: nil)
    let callActionHandler = {(action:UIAlertAction!)-> Void in
        let alertMessage = UIAlertController(title: "Service Unavaliable", message: "Sorry, the call is not avaliable yet, please retry later.", preferredStyle: .Alert)
        alertMessage.addAction(nocallAction)
    }
    //this is what happened after you hit the call option
    let callAction = UIAlertAction(title: "Call " + "123-000-\(indexPath.row)", style:
        UIAlertActionStyle.Default, handler: callActionHandler)
    //this is what happened after you hit the been there option
    let isVisitedAction = UIAlertAction(title: "I've been here", style: .Default, handler: {
        (action:UIAlertAction!) -> Void in
        let cell = tableView.cellForRowAtIndexPath(indexPath)
        cell?.accessoryType = .Checkmark
        })
    //add the action to the option menu
    optionMenu.addAction(isVisitedAction)
    optionMenu.addAction(callAction)
    optionMenu.addAction(cancelAction)

    self.presentViewController(optionMenu, animated: true, completion: nil)

}

Answer 1

您永远不会在callActionHandler中显示视图控制器-它应如下所示：

let callActionHandler = {(action:UIAlertAction!)-> Void in
    let alertMessage = UIAlertController(title: "Service Unavaliable", message: "Sorry, the call is not avaliable yet, please retry later.", preferredStyle: .Alert)
    alertMessage.addAction(nocallAction)

    self.presentViewController(alertMessage, animated: true, completion: nil)
}

Swift还允许您与UIAlertAction同时创建完成处理程序，我认为它更具可读性：

    let callAction = UIAlertAction(title: "Call " + "123-000-243534", style: UIAlertActionStyle.Default) 
    { action in
        let alertMessage = UIAlertController(title: "Service Unavaliable", message: "Sorry, the call is not avaliable yet, please retry later.", preferredStyle: .Alert)
        alertMessage.addAction(nocallAction)

        self.presentViewController(alertMessage, animated: true, completion: nil)
    }