如何在SWIFT中解除没有动作的UIAlertController？

Question

我的图像下载时显示UIAlertController.下载完成后,我想推送一个视图控制器.我在控制台中有错误,因为我没有关闭警报控制器:

pushViewController:animated: called on <UINavigationController 0x7fb190c6ee00> while an existing transition or presentation is occurring; the navigation stack will not be updated.

在我的主视图控制器中,当下载完成时,我推送另一个视图:

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

    //....

    var alert = UIAlertController(title: "Alert", message: text, preferredStyle: UIAlertControllerStyle.Alert)
    self.presentViewController(alert, animated: true, completion: nil)


    dispatch_async(dispatch_get_main_queue(), {
        if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
               self.performSegueWithIdentifier("postview", sender: self)

        }
   })
}

我尝试过dismissViewControllerAnimated,但我有完全相同的错误:

dispatch_async(dispatch_get_main_queue(), {
            if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
                   alert.dismissViewControllerAnimated(true, completion: nil)
                   self.performSegueWithIdentifier("postview", sender: self)

            }
       })

Answer 1

performSegueWithIdentifier在上一个视图控制器被解除之前,您不应该打电话.要正确计时,请从完成处理程序执行此操作:

dispatch_async(dispatch_get_main_queue(), {
    if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
       alert.dismissViewControllerAnimated(true, completion: {
           self.performSegueWithIdentifier("postview", sender: self)
       })
    }
})

现在执行segue的调用在解雇结束之前不会启动,从而防止您看到的错误.