快速发送到实例的无法识别的选择器

Question

我在代码中使用从一个视图控制器到另一个视图控制器的转场，它们都嵌入在导航控制器中，转场是“显示”。

这就是我所说的segue：

        performSegueWithIdentifier("LogIn", sender: self)

这就是我所做的：

 override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "LogIn"  {
            segue.destinationViewController.setShowsCancelButton(false, animated: false)
        }

    }

一旦触发 segue，我就会在 Xcode 中得到一个错误：

[Chooze.LogInOrRegisterViewController setShowsCancelButton:animated:]: unrecognized selector sent to instance 0x7f928b93aed0
2014-09-23 16:40:04.608 Chooze[9935:939290] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Chooze.LogInOrRegisterViewController setShowsCancelButton:animated:]: unrecognized selector sent to instance 0x7f928b93aed0'

Answer 1

由于目标视图控制器嵌入在导航控制器中，您的代码试图在导航控制器上调用setShowsCancelButton。相反，您应该访问导航控制器的topViewController 属性，并在它返回的对象上调用setShowsCancelButton，例如：

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!)
{
    if segue.identifier == "Login" {
        let navController = segue.destinationViewController as UINavigationController
        let controller = navController.topViewController as LoginOrRegisterViewController
        controller.setShowsCancelButton(false, animated: false)
    }
}