已经呈现的 iOS 8 Xcode 6.1 Swift prepareForSegue Controller (空)

Question

我收到以下警告:

Warning: Attempt to present StartViewController: 0x7ff418e1be30 on StartViewController: 0x7ff418c4ab50 which is already presenting (null)

我的代码:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // 1
    if segue.identifier == "Add" {

        let alertController: UIAlertController = UIAlertController(title: "Choices", message: nil, preferredStyle: UIAlertControllerStyle.ActionSheet)
        let cancelAction: UIAlertAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel, handler: nil)
        let button1action: UIAlertAction = UIAlertAction(title: "First Choice", style: UIAlertActionStyle.Default, handler: { (action: UIAlertAction!) -> () in
            self.performSegueWithIdentifier("first", sender: self)
        })
        let button2action: UIAlertAction = UIAlertAction(title: "Second choice", style: UIAlertActionStyle.Default, handler: { (action: UIAlertAction!) -> () in
            self.performSegueWithIdentifier("second", sender: self)
        })
        alertController.addAction(cancelAction)
        alertController.addAction(button1action)
        alertController.addAction(button2action)


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

    }

如果我按下 ViewController 中的“添加”按钮，将会弹出警报，同时也会弹出警告消息。 Controller 在代码的最后一行调用自己，但我没有解决办法。有人可以帮助我吗？

Answer 1

如果您处于 prepareForSegue 中，则意味着您已经触发了 segue，因此某些 View Controller 的呈现已经开始。

您不应该从 prepareFromSegue 调用 presentViewController，而应使用它来设置 destination View Controller 。

对于这种情况，我认为当您添加时，您需要触发IBAction并将该代码移动到那里，而不是触发segue。