如何防止导航到 UIViewController 检查条件？

Question

我有一个显示视图控制器 (ViewControllerIncluirItem) 的按钮。但是，我需要在导航之前检查一个条件，我尝试在 func override func prepare(for segue: UIStoryboardSegue, sender: Any?) 中检查这个。但是，导航以任何方式发生。我试过这个：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "SegueToVcIncluirItem" {

            if pricelist != nil {
                print("pricelist ok")              
            } else {
                print("selecione pricelist")
                return // Here I want prevent.
            }

            let nav = segue.destination as! UINavigationController
            let childVc = nav.topViewController as! ViewControllerIncluirItem
            childVc.strTeste = "testado com sucesso"
        }
    }

Answer 1

您可以在方法shouldPerformSegue(withIdentifier:sender:)

中查看您的情况

您的代码应如下所示：

    func shouldPerformSegue(withIdentifier identifier: String,
                            sender: Any?) -> Bool{

        if identifier == "SegueToVcIncluirItem" {
           return pricelist != nil
        }

        return true
    }

Answer 2

func prepare(for segue: UIStoryboardSegue, sender: Any?) 在您要求调用时被调用。您必须使用这个：

self.performSegue(withIdentifier: "", sender: nil)

您要输入的条件 func prepare(for segue: UIStoryboardSegue, sender: Any?)，您应该在调用之前输入。所以应该是：

if pricelist != nil {
    print("pricelist ok")   
    self.performSegue(withIdentifier: "", sender: nil) 
} else {
    print("selecione pricelist")
}

现在您的 prepare 函数应该看起来非常简单：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let nav = segue.destination as! UINavigationController
        let childVc = nav.topViewController as! ViewControllerIncluirItem
        childVc.strTeste = "testado com sucesso"
}

如何防止导航到 UIViewController 检查条件？

How to prevent navigation to UIViewController checking a condition?

xcode

uinavigationcontroller

ios

uistoryboardsegue

swift