不能在工作表修饰符SwiftUI中使用状态变量吗？

Question

当我选择一个单元格时，我只需设置selectedPlayer对象并切换布尔值以显示对话框。

当激活工作表修饰符时，有以下几个问题：

1. selectedPlayer为零
2. ，片材改性剂称为4倍
3. ，纸张为4倍

。

我做错了什么？我猜身体会重新生成两次，因为我修改了两个状态变量，但是为什么selectedPlayer不正确，为什么修饰符被调用了4次？

struct PlayerListingView: View {

    @State private var selectedPlayer: PlayerEntity?
    @State private var showAddPlayer: Bool = false
    
    var body: some View {
        Section {
            ForEach(players) { player in
                playerCell(player, onSelect: { p in
                    selectedPlayer = p
                    printv("cell selected selectedPlayer: \(selectedPlayer)")
                    showAddPlayer.toggle()
                })
            }
        }
        .sheet(isPresented: $showAddPlayer) {
            printv("selectedPlayer: \(selectedPlayer)")
            EditPlayerView(isPresented: $showAddPlayer, player: selectedPlayer)
        }
    }

结果是：

cell selected selectedPlayer: Optional(<PlayerEntity: 0x600001a46440> (entity: PlayerEntity; id: 0xd30220ea8e2e9274 <x-coredata://3BBD8F8D-C878-4108-80BF-02ADECE684C2/PlayerEntity/p1>; data: {
    email = "my email";
    games = "<relationship fault: 0x60000393f180 'games'>";
    id = "BDB08E37-16B4-4372-9D31-18220405E1B1";
    "name_" = "my name";
    teams = "<relationship fault: 0x60000393f160 'teams'>";
}))
selectedPlayer: nil
selectedPlayer: nil
selectedPlayer: nil
selectedPlayer: nil
2021-10-22 08:59:41.845954-0500 app[75686:6355985] Writing analzed variants.
2021-10-22 08:59:42.447861-0500 app[75686:6355985] [Presentation] Attempt to present <_TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView_: 0x7ff21b718230> on <_TtGC7SwiftUI19UIHostingControllerGVS_15ModifiedContentVS_7AnyViewVS_12RootModifier__: 0x7ff1fc007150> (from <_TtGC7SwiftUI19UIHostingControllerGVS_15ModifiedContentGS1_VVS_22_VariadicView_Children7ElementVS_24NavigationColumnModifier_GVS_18StyleContextWriterVS_19SidebarStyleContext___: 0x7ff21b70c8e0>) which is already presenting <_TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView_: 0x7ff21d323ac0>.
2021-10-22 08:59:42.448226-0500 app[75686:6355985] [Presentation] Attempt to present <_TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView_: 0x7ff21b719c80> on <_TtGC7SwiftUI19UIHostingControllerGVS_15ModifiedContentVS_7AnyViewVS_12RootModifier__: 0x7ff1fc007150> (from <_TtGC7SwiftUI19UIHostingControllerGVS_15ModifiedContentGS1_VVS_22_VariadicView_Children7ElementVS_24NavigationColumnModifier_GVS_18StyleContextWriterVS_19SidebarStyleContext___: 0x7ff21b70c8e0>) which is already presenting <_TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView_: 0x7ff21d323ac0>.
2021-10-22 08:59:42.448574-0500 app[75686:6355985] [Presentation] Attempt to present <_TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView_: 0x7ff21d326920> on <_TtGC7SwiftUI19UIHostingControllerGVS_15ModifiedContentVS_7AnyViewVS_12RootModifier__: 0x7ff1fc007150> (from <_TtGC7SwiftUI19UIHostingControllerGVS_15ModifiedContentGS1_VVS_22_VariadicView_Children7ElementVS_24NavigationColumnModifier_GVS_18StyleContextWriterVS_19SidebarStyleContext___: 0x7ff21b70c8e0>) which is already presenting <_TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView_: 0x7ff21d323ac0>.

Answer 1

您可以通过切换布尔值来呈现工作表。

func sheet<Content>(isPresented: Binding<Bool>,...

或者通过选择一项

func sheet<Item, Content>(item: Binding<Item?>,...

但不是同时发生的。如果要继续进行所选项，请只使用(后一种形式的)并删除Bool

struct PlayerListingView: View {

    @State private var selectedPlayer: PlayerEntity?
    
    var body: some View {
        Section {
            ForEach(players) { player in
                playerCell(player, onSelect: { p in
                    selectedPlayer = p
                    printv("cell selected selectedPlayer: \(selectedPlayer)")
                  
                })
            }
        }
        .sheet(item: $selectedPlayer) {
            printv("selectedPlayer: \(selectedPlayer)")
            EditPlayerView(player: selectedPlayer)
        }
    }

Answer 2

最后，基于@vadian的反馈，我做了这样的事情：

struct PlayerListingView: View {
    @FetchRequest var players: FetchedResults<PlayerEntity>

    @Environment(\.managedObjectContext) private var managedObjectContext

    @State private var selectedPlayer: PlayerEntity?
    @State private var showAddPlayer: Bool = false

    init() {
        _players = FetchRequest(fetchRequest: PlayerEntity.fetchRequestWithPredicate())
    }
    
    var body: some View {
        Section(header) {
            ForEach(players) { player in
                playerCell(player, onSelect: { p in
                    selectedPlayer = p
                })
            }
        }
        .sheet(item: $selectedPlayer) { item in
            EditPlayerView(player: item) {
                selectedPlayer = nil
            }
        }
        .sheet(isPresented: $showAddPlayer) {
            EditPlayerView(player: nil) {
                showAddPlayer.toggle()
            }
        }
    }

    ...
}