Início / coding / Perguntas / 79583787
Accepted
GT4485
Asked: 2025-04-21 05:59:22 +0800 CST

Aplicativo SwiftUI para MacOS: a vinculação de alternância para modelView em subvisualizações não funciona

  • 772

Minha ContentView principal contém uma ChecklistView, que contém várias CheckViews, que por sua vez contêm uma Toggle view. Ao clicar em uma caixa de seleção, as informações são passadas para o ContentViewModel, mas não retornam para as subViews. Como posso corrigir isso? Estou usando o Xcode 16.3, com Swift 5 ou Swift 6: sem diferença. O código unido foi projetado para testar diferentes estruturas de declaração de view.

import SwiftUI
@main
struct TestCheckListApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView(cvm: ContentViewModel())
        }
    }
}

import SwiftUI
final class ChecklistItem: Identifiable, ObservableObject
{
    let id = UUID()
    var title: String
    var isChecked: Bool
    
    init(title: String, isChecked: Bool = false) {
        self.title = title
        self.isChecked = isChecked
    }
    func toggle() { isChecked.toggle() }
}

import SwiftUI
final class ContentViewModel: ObservableObject {
    @Published var report: String = ""
    @Published var arrItem: [ChecklistItem] = [
        ChecklistItem(title: "Item 0"),
        ChecklistItem(title: "Item 1"),
        ChecklistItem(title: "Item 2")
    ]
    func buttonTapped()
    {
        var s: String = ""
        for item in arrItem
        {
            s += "\(item.title) : \(item.isChecked), "
            print("\(item.title) : \(item.isChecked)")
        }
        report = s
    }
}

import SwiftUI
struct ContentView: View {
    @ObservedObject var cvm: ContentViewModel
    @State private var multiSelection = Set<UUID>()
    var body: some View {
        VStack(alignment: .leading) {
            HStack {
                Button(action: cvm.buttonTapped) {
                    Text("Display values in view model")
                }
                Text(cvm.report)
            }
            Divider()
            HStack {
                Text("Toggles in ContentView:")
                Toggle(cvm.arrItem[0].title, isOn: $cvm.arrItem[0].isChecked)
                Toggle(cvm.arrItem[1].title, isOn: $cvm.arrItem[1].isChecked)
                Toggle(cvm.arrItem[2].title, isOn: $cvm.arrItem[2].isChecked)
            }
            Divider()
            HStack {
                Text("Toggles in CheckView in ContentView:")
                CheckView(cli: cvm.arrItem[0])
                CheckView(cli: cvm.arrItem[1])
                CheckView(cli: cvm.arrItem[2])
            }
            Divider()
            Text("Toggles in List in ContentView:")
            List {
                ForEach($cvm.arrItem) { item in
                    Toggle("item.title", isOn: item.isChecked)                    }
            }
            Divider()
            Text("Toggles in ChecklistView:")
            ChecklistView(cl: cvm.arrItem)
        }
        .padding()
        .preferredColorScheme(.light)
    }
}
#Preview {
    ContentView(cvm: ContentViewModel())
}

import SwiftUI
struct CheckView: View {
    @ObservedObject var cli: ChecklistItem
    var body: some View {
        Toggle(cli.title, isOn: $cli.isChecked)
    }
}

#Preview {
    CheckView(cli: ContentViewModel().arrItem[0])
}

import SwiftUI
struct ChecklistView : View {
    var cl: [ChecklistItem]
    var body: some View {
        List {
            ForEach(cl) { item in
                CheckView(cli: item)
            }
        }
    }
}
#Preview {
    ChecklistView(cl: ContentViewModel().arrItem)
}
macos

2 respostas

  1. Best Answer

    Se você realmente deseja continuar usando final class ContentViewModel: ObservableObject, altere seu final class ChecklistItempara a struct ChecklistItem e certifique-se de passar uma vinculação quando quiser alterá-lo. Além disso, você precisa declarar uma única fonte de verdade de dados para seu ContentViewModel.

    Código de exemplo, testado em dispositivo real, não em visualizações:

    
@main
struct TestCheckListApp: App {
    @StateObject private var cvm = ContentViewModel()  // <-- here
    
    var body: some Scene {
        WindowGroup {
            ContentView(cvm: cvm)  // <-- here
        }
    }
}

struct ChecklistItem: Identifiable {  // <-- here
    let id = UUID()
    var title: String
    var isChecked: Bool
    
    init(title: String, isChecked: Bool = false) {
        self.title = title
        self.isChecked = isChecked
    }
}

final class ContentViewModel: ObservableObject {
    @Published var report: String = ""
    @Published var arrItem: [ChecklistItem] = [
        ChecklistItem(title: "Item 0"),
        ChecklistItem(title: "Item 1"),
        ChecklistItem(title: "Item 2")
    ]
    
    func buttonTapped()
    {
        var s: String = ""
        for item in arrItem
        {
            s += "\(item.title) : \(item.isChecked), "
            print("\(item.title) : \(item.isChecked)")
        }
        report = s
    }
}

struct ContentView: View {
    @ObservedObject var cvm: ContentViewModel
    @State private var multiSelection = Set<UUID>()
    
    var body: some View {
        VStack(alignment: .leading) {
            HStack {
                Button(action: cvm.buttonTapped) {
                    Text("Display values in view model")
                }
                Text(cvm.report)
            }
            Divider()
            HStack {
                Text("Toggles in ContentView:")
                Toggle(cvm.arrItem[0].title, isOn: $cvm.arrItem[0].isChecked)
                Toggle(cvm.arrItem[1].title, isOn: $cvm.arrItem[1].isChecked)
                Toggle(cvm.arrItem[2].title, isOn: $cvm.arrItem[2].isChecked)
            }
            Divider()
            HStack {
                Text("Toggles in CheckView in ContentView:")
                CheckView(cli: $cvm.arrItem[0])  // <-- here
                CheckView(cli: $cvm.arrItem[1])
                CheckView(cli: $cvm.arrItem[2])
            }
            Divider()
            Text("Toggles in List in ContentView:")
            List {
                ForEach($cvm.arrItem) { $item in  // <-- here
                    Toggle("item.title", isOn: $item.isChecked)  // <-- here
                }
            }
            Divider()
            Text("Toggles in ChecklistView:")
            ChecklistView(cl: $cvm.arrItem)  // <-- here
        }
        .padding()
        .preferredColorScheme(.light)
    }
}

struct CheckView: View {
    @Binding var cli: ChecklistItem  // <-- here

    var body: some View {
        Toggle(cli.title, isOn: $cli.isChecked)  // <-- here
    }
}

struct ChecklistView : View {
    @Binding var cl: [ChecklistItem]  // <-- here
    
    var body: some View {
        List {
            ForEach($cl) { $item in  // <-- here
                CheckView(cli: $item)  // <-- here
            }
        }
    }
}
    • 1 
  2. import SwiftUI
@main
struct TestChecklistObsEnvApp: App {
    @State private var cvm = ContentViewModel()
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(cvm)
        }
    }
}
//============
struct ChecklistItem: Identifiable {
    let id = UUID()
    var title: String
    var isChecked: Bool
    
    init(title: String, isChecked: Bool = false) {
        self.title = title
        self.isChecked = isChecked
    }
}
//============
@Observable final class ContentViewModel {
    var report: String = ""
    var arrItem: [ChecklistItem] = [
        ChecklistItem(title: "Item 0"),
        ChecklistItem(title: "Item 1"),
        ChecklistItem(title: "Item 2")
    ]
    
    func buttonTapped()
    {
        var s: String = ""
        for item in arrItem
        {
            s += "\(item.title) : \(item.isChecked), "
            print("\(item.title) : \(item.isChecked)")
        }
        report = s
    }
}
//============
struct ContentView: View {
    @Environment(ContentViewModel.self) private var cvm
    @State private var multiSelection = Set<UUID>()
    
    var body: some View {
        @Bindable var cvm = cvm
        VStack(alignment: .leading) {
            Text("Version migrated from ObservableObject to @Observable, with use of @Environment")
                .font(.title)
            HStack {
                Button(action: cvm.buttonTapped) {
                    Text("Display values in view model")
                }
                Text(cvm.report)
            }
            Divider()
            HStack {
                Text("Toggles in ContentView:")
                Toggle(cvm.arrItem[0].title, isOn: $cvm.arrItem[0].isChecked)
                Toggle(cvm.arrItem[1].title, isOn: $cvm.arrItem[1].isChecked)
                Toggle(cvm.arrItem[2].title, isOn: $cvm.arrItem[2].isChecked)
            }
            Divider()
            HStack {
                Text("Toggles in CheckView in ContentView:")
                CheckView(cli: $cvm.arrItem[0])
                CheckView(cli: $cvm.arrItem[1])
                CheckView(cli: $cvm.arrItem[2])
            }
            Divider()
            Text("Toggles in List in ContentView:")
            List {
                ForEach($cvm.arrItem) { $item in  // <-- here
                    Toggle(item.title, isOn: $item.isChecked)
                }
            }
            Divider()
            Text("Toggles in ChecklistView:")
            ChecklistView(cl: $cvm.arrItem)
        }
        .padding()
        .preferredColorScheme(.light)
    }
}
//============
struct CheckView: View {
    @Binding var cli: ChecklistItem

    var body: some View {
        Toggle(cli.title, isOn: $cli.isChecked)
    }
}
//============
struct ChecklistView : View {
    @Binding var cl: [ChecklistItem]
    
    var body: some View {
        List {
            ForEach($cl) { $item in
                CheckView(cli: $item)
            }
        }
    }
}
    • 0

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