如何将一个SwiftUI View作为变量传递给另一个View结构 [英] How to pass one SwiftUI View as a variable to another View struct

问题描述

我正在实现名为MenuItem的非常自定义NavigationLink，并希望在整个项目中重复使用它.这是一个符合View并实现包含NavigationLink的var body : some View的结构. 我需要以某种方式将应由NavigationLink呈现的视图存储在MenuItem的正文中，但尚未这样做.

I'm implementing a very custom NavigationLink called MenuItem and would like to reuse it across the project. It's a struct that conforms to View and implements var body : some View which contains a NavigationLink. I need to somehow store the view that shall be presented by NavigationLink in the body of MenuItem but have yet failed to do so.

我在MenuItem的主体中将destinationView定义为some View，并尝试了两个初始化程序:

I have defined destinationView in MenuItem's body as some View and tried two initializers:

这似乎太简单了:

struct MenuItem: View {
    private var destinationView: some View

    init(destinationView: View) {
        self.destinationView = destinationView
    }

    var body : some View {
        // Here I'm passing destinationView to NavigationLink...
    }
}

->错误::协议视图"仅具有通用或相关类型要求，因此只能用作通用约束.

--> Error: Protocol 'View' can only be used as a generic constraint because it has Self or associated type requirements.

第二次尝试:

struct MenuItem: View {
    private var destinationView: some View

    init<V>(destinationView: V) where V: View {
        self.destinationView = destinationView
    }

    var body : some View {
        // Here I'm passing destinationView to NavigationLink...
    }
}

->错误:无法将类型为"V"的值分配为类型为某些视图".

--> Error: Cannot assign value of type 'V' to type 'some View'.

最终尝试:

struct MenuItem: View {
    private var destinationView: some View

    init<V>(destinationView: V) where V: View {
        self.destinationView = destinationView as View
    }

    var body : some View {
        // Here I'm passing destinationView to NavigationLink...
    }
}

->错误::无法将视图"类型的值分配给某些视图".

--> Error: Cannot assign value of type 'View' to type 'some View'.

我希望有人能帮助我.如果NavigationLink可以接受某些View作为参数，则必须有一种方法. 谢谢; D

I hope someone can help me. There must be a way if NavigationLink can accept some View as an argument. Thanks ;D

推荐答案

总结一下我在这里阅读的所有内容以及在 iOS14 上适用于我的解决方案:

To sum up everything I read here and the solution which worked for me and on iOS14:

struct ContainerView<Content: View>: View {
    let content: Content

    init(@ViewBuilder content: @escaping () -> Content) {
        self.content = content()
    }
    
    var body: some View {
        // Do something with `content`
    }
}

这不仅允许您将简单的View放入其中，而且由于@ViewBuilder的原因，还可以使用if-else和switch-case块:

This not only allows you to put simple Views inside, but also, thanks to @ViewBuilder, use if-else and switch-case blocks:

struct SimpleView: View {
    var body: some View {
        ContainerView {
            Text("SimpleView Text")
        }
    }
}

struct IfElseView: View {
    var flag = true
    
    var body: some View {
        ContainerView {
            if flag {
                Text("True text")
            } else {
                Text("False text")
            }
        }
    }
}

struct SwitchCaseView: View {
    var condition = 1
    
    var body: some View {
        ContainerView {
            switch condition {
            case 1:
                Text("One")
            case 2:
                Text("Two")
            default:
                Text("Default")
            }
        }
    }
}

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