SwiftUI中Switch选子视图时WrapperView的any View报错解决

我定义了一个接收遵循View协议的子视图的WrapperView结构体：

struct WrapperView<C: View>: View {
    let childView: C

    init(_ childView: () -> (C)) {
        self.childView = childView()
    }

    var body: some View {
        childView
    }
}

另外我有一个RealView结构体，其bodyView函数根据条件返回封装后的子视图：

struct TextAView: View {
    var body: some View {
        Text("A")
    }
}

struct TextBView: View {
    var body: some View {
        Text("B")
    }
}

struct TextCView: View {
    var body: some View {
        Text("C")
    }
}

struct RealView: View {    
    var body: some View {
        bodyView()
    }
    
    private func bodyView() -> some View {
        let type = 1
        
        var bodyChild: any View
        
        switch type {
        case 1:
            bodyChild = TextAView()
        case 2:
            bodyChild = TextBView()
        case 3:
            bodyChild = TextCView()
        default:
            bodyChild = EmptyView()
        }
        
        return WrapperView {
            //Text("Hello") <- 此处正常运行
            bodyChild // <- 报错：Type 'any View' cannot conform to 'View'
        }
    }
}

已知报错原因是bodyChild的类型为any View，但编译器要求传入具体的View类型。请问如何修改才能实现根据条件返回bodyChild并正常完成封装？

方案1：直接在Switch分支返回WrapperView #

不需要先存储any View类型的变量，直接在每个case分支中生成对应子视图并传入WrapperView，编译器会自动推导每个分支的具体泛型类型，最终通过some View统一返回：

struct RealView: View {    
    var body: some View {
        bodyView()
    }
    
    private func bodyView() -> some View {
        let type = 1
        
        switch type {
        case 1:
            return WrapperView { TextAView() }
        case 2:
            return WrapperView { TextBView() }
        case 3:
            return WrapperView { TextCView() }
        default:
            return WrapperView { EmptyView() }
        }
    }
}

方案2：用AnyView做类型擦除 #

如果需要保留存储bodyChild的逻辑，可以用AnyView对any View进行类型擦除，将其转换为具体的View类型传入WrapperView：

struct RealView: View {    
    var body: some View {
        bodyView()
    }
    
    private func bodyView() -> some View {
        let type = 1
        
        var bodyChild: any View
        
        switch type {
        case 1:
            bodyChild = TextAView()
        case 2:
            bodyChild = TextBView()
        case 3:
            bodyChild = TextCView()
        default:
            bodyChild = EmptyView()
        }
        
        return WrapperView {
            AnyView(bodyChild)
        }
    }
}

方案3：修改WrapperView支持any View #

如果不需要依赖泛型的具体类型，可以直接修改WrapperView的定义，让它接受any View类型的子视图：

struct WrapperView: View {
    let childView: any View

    init(_ childView: () -> any View) {
        self.childView = childView()
    }

    var body: some View {
        childView
    }
}

修改后原RealView的代码无需调整，直接传入bodyChild即可正常编译。

方案4：利用@ViewBuilder简化逻辑 #

使用@ViewBuilder属性包装器自动处理不同分支的视图类型差异，代码更简洁：

struct RealView: View {    
    var body: some View {
        bodyView()
    }
    
    @ViewBuilder
    private func bodyView() -> some View {
        let type = 1
        
        switch type {
        case 1:
            WrapperView { TextAView() }
        case 2:
            WrapperView { TextBView() }
        case 3:
            WrapperView { TextCView() }
        default:
            WrapperView { EmptyView() }
        }
    }
}

内容的提问来源于stack exchange，提问作者Kunal Shah