ios - 在我快速按下按钮后，在 segue 之前执行一些代码

Question

我有一个转到另一个 View 的按钮。我想在 segue 移动之前执行一些代码。我面临的问题是 segue 在代码有机会完成之前转到另一页。因此，在 View 更改之前，用户默认值中的值不会更改。我的问题是如何让代码运行并在它完成后让 segue 触发？这是我目前所拥有的:

 @IBAction func onLogoutClick(sender: AnyObject) {
    //clear all url chache 
    NSURLCache.sharedURLCache().removeAllCachedResponses()
    //null out everything for logout
    email = ""
    password = ""
    self.loginInformation.setObject(self.email, forKey: "email")
    self.loginInformation.setObject(self.password, forKey: "password")
    self.loginInformation.synchronize()
    //self.view = LoginView
}

Answer 1

你有几个选择；

首先是从 IB 中的按钮中删除操作，然后在 UIViewController 对象和您的下一个场景之间创建一个转场；

@IBAction func onLogoutClick(sender: AnyObject) {
    //clear all url chache 
    NSURLCache.sharedURLCache().removeAllCachedResponses()
    //null out everything for logout
    email = ""
    password = ""
    self.loginInformation.setObject(self.email, forKey: "email")
    self.loginInformation.setObject(self.password, forKey: "password")
    self.loginInformation.synchronize()

    self.performSegueWithIdentifier("logoutSegue",sender: self)
}

或者你可以摆脱@IBAction方法并实现prepareForSegueWithIdentifier

override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
   if segue.identifier == "logoutSegue"  {
        //clear all url chache 
        NSURLCache.sharedURLCache().removeAllCachedResponses()
        //null out everything for logout
        email = ""
        password = ""
        self.loginInformation.setObject(self.email, forKey: "email")
        self.loginInformation.setObject(self.password, forKey: "password")
        self.loginInformation.synchronize()
   }
}