ios - 无法使用 xcode beta 6.3 将 View Controller 推送到导航 Controller

Question

我正在尝试将 View Controller 推送到导航 Controller 中。该代码在 xcode 6.1 中似乎是正确的。但是当我将项目更改为 xcode beta6.3 时，xcode 要求我将类型运算符更改为 as!。现在我无法将 View Controller 推送到导航 Controller 中

//delegate method
    func sendIndex(row : Int){

        switch row {

        case 0:

            if(!isCurrentMoneyVc){
            let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
            let moneySummaryVC: MoneySummaryVC = storyboard.instantiateViewControllerWithIdentifier("moneyVC") as MoneySummaryVC
            //self.navigationController?.pushViewController(moneySummaryVC, animated: true)
            self.navigationController?.setViewControllers([moneySummaryVC], animated: true)
            }else{
                hideMenu()
            }

        case 1:

            if(!isCurrentAboutVc){
            let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
            let moneySummaryVC1: AccountsVC = storyboard.instantiateViewControllerWithIdentifier("account") as AccountsVC

            self.navigationController?.pushViewController(moneySummaryVC1, animated: true)
            }else{
                hideMenu()
            }

        case 2:

            if(!isCurrentTransactionVc){
            let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
            let moneySummaryVC2: Transaction = storyboard.instantiateViewControllerWithIdentifier("transact") as Transaction
            self.navigationController?.pushViewController(moneySummaryVC2, animated: true)
            }else{
                hideMenu()
            }

        default:
            println("no index")


        }

    }

Answer 1

从技术上讲，如果在 Storyboard 中找不到，您的 viewcontroller 可以为 nil，这可能是 xcode 提示的原因。从 Storyboard 中引用 View Controller 并推送它的更好方法:

if let moneySummaryVC2 = storyboard.instantiateViewControllerWithIdentifier("transact") as? Transaction {
        self.navigationController?.pushViewController(moneySummaryVC2, animated: true)
}

现在我们只在成功创建 View Controller 常量 moneySummaryVC2 时尝试推送 View Controller ，这意味着在 Storyboard中找到了 View Controller ID。不要忘记处理未找到 View Controller 的情况(日志记录或其他)。