ios - UIAlertController 错误在 swift 模式呈现的 View Controller 中调用时

Question

我有一个以模态方式呈现的 View Controller ，当我运行 UIAlertController 时，不断收到错误消息。我该如何解决这个问题。

警报由检查文本字段是否为空的按钮触发。

@IBAction func registerAction(sender: AnyObject) {
if(userEmail.isEmpty){
        alertMessage("Fields Are Empty")
    }
}



func alertMessage(userMessage:String){  
    var myAlert = UIAlertController(title: "Alert", message: userMessage, preferredStyle: UIAlertControllerStyle.Alert)
    let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil)
    myAlert.addAction(okAction)
    self.presentViewController(myAlert, animated: true, completion: nil)
}

当我运行警报时出错

Warning: Attempt to present <UIAlertController: 0x7f9bbb9060d0>  on <AlertApp.CustomSignupVC: 0x7f9bb94accb0> which is already presenting <UIAlertController: 0x7f9bbb926660>

Answer 1

尝试将其添加到主操作队列中。

dispatch_async(dispatch_get_main_queue()) {
    self.presentViewController(myAlert, animated: true, completion: nil)
}

检查这个相关问题:Presenting a view controller modally from an action sheet's delegate in iOS8 - iOS10