ios - 无法将 PageViewController 类型的值转换为另一个 Controller

Question

你好，我有ViewController，它通过segue连接到UIPageViewController，并且在ViewController中还有两个按钮通过segue连接到另一个 Controller (LoginSignupViewController)。按钮名称为“登录”和“注册”。登录和注册按钮都有不同的 segue 标识符。我在单击“登录”按钮或“注册”按钮时遇到错误

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
    if (segue.identifier == "loginSegue") {

        let secondViewController = segue.destinationViewController as! LoginSignupViewController

        secondViewController.navigationTitle = "LOGIN"

    }else if (segue.identifier == "registerSegue") {

        let secondViewController = segue.destinationViewController as! LoginSignupViewController

        secondViewController.navigationTitle = "SIGN UP"
        //etc...
    }

}

如果我使用此代码编译应用程序..我得到这个

Terminating app due to uncaught exception 'NSInvalidArgumentException' reason: '-[__NSCFType set]: unrecognized selector sent to instance

所以我删除了 if else 条件并使用此代码编译了应用程序

let secondViewController = segue.destinationViewController as!   LoginSignupViewController

    secondViewController.navigationTitle = "LOGIN"

我收到此错误

 Could not cast value of type 'Myproject.PageViewController' (0x10008c550) to 'MyProject.LoginSignupViewController' (0x10008c0f0).

当我打印出print(segue.identifier)

它在控制台上打印此内容

Optional("pageViewController")

我的 Storyboard截图

注意:该代码在 IOS 9 或更高版本上运行良好。应用程序在 IOS 8.4 上崩溃

Answer 1

我看到你的问题了。您应该保留 if-else 条件。你应该这样做:

1 将 var stringTitle: String! 放入 LoginSignupViewController

2 将 prepareSegue 中的代码更改为:

if (segue.identifier == "loginSegue") {

    let secondViewController = segue.destinationViewController as! LoginSignupViewController

    secondViewController.stringTitle = "LOGIN"

}else if (segue.identifier == "registerSegue") {

    let secondViewController = segue.destinationViewController as! LoginSignupViewController

    secondViewController.stringTitle = "SIGN UP"
    //etc...
}

3在LoginSignupViewController的viewDidLoad中放置代码:

self.navigationItem.title = "LOGIN"