Question

我以编程方式编写UI，现在我想从情节提要中添加ui，当我尝试这样做时，编译器会说“在展开可选值时意外发现nil”

在情节提要中-> ViewController->自定义类我设置了我的类。我也设置了ID“ board1” 为什么要设置nil值？

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        table.deselectRow(at: indexPath, animated: true)
        let registerViewController = storyboard?.instantiateViewController(withIdentifier: "board1") as? RegisterViewController
        present(registerViewController!, animated: true, completion: nil)
    }

Answer 1

您似乎在此处使用storyboard的一些未知实例：

let registerViewController = storyboard?.instantiateViewController(withIdentifier: "board1") as? RegisterViewController

根据您的评论，storyboard似乎不是您声明的。这意味着它可能没有引用您的Main.storyboard文件，甚至可能为零。

您应该创建一个引用您的UIStoryboard文件的新Main.storyboard实例，如下所示：

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let registerViewController = storyboard.instantiateViewController(withIdentifier: "board1") as? RegisterViewController

Answer 2

您可以这样做：

// Perform the segue to the viewController you want. Make sure you set the identifier the same as in the storyboard

let VC1 = (self.storyboard?.instantiateViewController(withIdentifier: "yourIdentifier"))!
self.present(VC1, animated: true, completion: nil)

也可以为此编写扩展名：

extension UIViewController {
    func presentView(withIdentifier: String) {
        if let newVC = self.storyboard?.instantiateViewController(withIdentifier: withIdentifier) {
        self.present(newVC, animated: true, completion: nil)
        }
    }
}

然后这样称呼

self.presentView(withIdentifier: "yourIdentifier")

故事板如何呈现课堂

2 个答案: