SwiftUI:有条件地显示不同的工作表项目 [英] SwiftUI: show different sheet items conditionally

问题描述

我在尝试如何使用 .sheet(item:content:) 时失败了.我知道这里和其他平台上有很多信息，但我无法让它发挥作用...

I am failing miserably trying to wrap my head around how to use .sheet(item:content:). I know that there is a lot of information here and on other platforms, but I just cannot get it to work...

这是我想要的视图的抽象——我不知道我在这里做错了什么:

Here's an abstraction of the view I'd like to have – and I don't know what I am doing wrong here:

import SwiftUI

enum SheetView: String, Identifiable {
    var id: Self { self }
    case sheetA = "Sheet A"
    case sheetB = "Sheet B"
}

struct SheetViewTest: View {
    @State private var showSheet: SheetView? = nil
    
    var body: some View {
        Form {
            Button(action: {
                showSheet = .sheetA
                print("Button \(showSheet?.rawValue) tapped…")
            }, label: {
                Text(SheetView.sheetA.rawValue)
            })
            Button(action: {
                showSheet = .sheetB
                print("Button \(showSheet?.rawValue) tapped…")
            }, label: {
                Text(SheetView.sheetB.rawValue)
            })
        }
        .sheet(item: $showSheet) { sheet -> View in
            Text(sheet.rawValue)
        }
    }
}

struct SheetViewTest_Previews: PreviewProvider {
    static var previews: some View {
        SheetViewTest()
    }
}

我在身体上的错误如下:协议类型'View'的值不能符合'View'；只有 struct/enum/class 类型可以符合协议，这是由于 .sheet 修饰符导致当我将其注释掉时，视图工作正常...

The error I am on the body getting is as follows: Value of protocol type 'View' cannot conform to 'View'; only struct/enum/class types can conform to protocols, which is due to the .sheet modifier cause when I comment it out, the view works just fine...

推荐答案

只需移除闭包返回类型(从返回的内容中自动推断)，即

Just remove closure return type (which is inferred automatically from returned content), i.e.

    .sheet(item: $showSheet) { sheet in      // << here !!
        Text(sheet.rawValue)
    }

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