@State var 不存储值

Question

我的目标是在视图之间传递值，从 Chooser 到 ThemeEditor。当用户按下一个图标时，我将保存我想要传递的对象，稍后使用 sheet 并传递包含 @State var.

内容的新创建的视图

已成功分配给 @State var themeToEdit，但是在 sheet

中创建 ThemeEditor 视图时它是 nil

我做错了什么？

struct Chooser: View {
    @EnvironmentObject var store: Store
    
    @State private var showThemeEditor = false
    @State private var themeToEdit: ThemeContent?
    @State private var editMode: EditMode = .inactive
    @State private var isValid = false
    
    var body: some View {
        
        NavigationView {
            List {
                ForEach(self.store.games) { game in
                    NavigationLink(destination: gameView(game))
                    {
                        Image(systemName: "wrench.fill")
                            .imageScale(.large)
                            .opacity(editMode.isEditing ? 1 : 0)
                            .onTapGesture {
                                self.showThemeEditor = true
                                /* themeInfo is of type struct ThemeContent: Codable, Hashable, Identifiable */
                                self.themeToEdit = game.themeInfo 
                            }
                        VStack (alignment: .leading) {
                            Text(self.store.name(for: something))
                                
                            HStack{
                                /* some stuff */
                                Text(" of: ")
                                Text("Interesting info")
                            }
                        }
                    }
                }
                .sheet(isPresented: $showThemeEditor) {
                    if self.themeToEdit != nil { /* << themeToEdit is nil here - always */
                        ThemeEditor(forTheme: self.themeToEdit!, $isValid)
                    } 
                }
            }
            .environment(\.editMode, $editMode)
        }
    }
}


struct ThemeEditor: View {
    @State private var newTheme: ThemeContent
    @Binding var isValid: Bool
    @State private var themeName = ""
    
    init(forTheme theme: ThemeContent, isValid: Binding<Bool>) {
        self._newTheme = State(wrappedValue: theme)
        self._validThemeEdited = isValid
    }
    var body: some View {
           ....
    }
}

struct ThemeContent: Codable, Hashable, Identifiable {
/* stores simple typed variables of information */
}

Answer 1

.sheet内容视图是在创建时捕获的，所以如果你想检查里面的东西，你需要使用.sheet(item:)变体，比如

.sheet(item: self.$themeToEdit) { item in
    if item != nil {
        ThemeEditor(forTheme: item!, $isValid)
    } 
}

注意：不清楚什么是 ThemeContent，但可能需要使其符合其他协议。

Answer 2

使用Binding。用这个改变你的 ThemeEditor 视图。

struct ThemeEditor: View {
    @Binding private var newTheme: ThemeContent?
    @Binding var isValid: Bool
    @State private var themeName = ""
    
    init(forTheme theme: Binding<ThemeContent?>, isValid: Binding<Bool>) {
        self._newTheme = theme
        self._isValid = isValid
    }
    var body: some View {
        ....
    }
}

以及 sheet 代码

.sheet(isPresented: $showThemeEditor) {
    ThemeEditor(forTheme: $themeToEdit, isValid: $isValid)
}

正在行动

.onTapGesture {
    /* themeInfo is of type struct ThemeContent: Codable, Hashable, Identifiable */
    self.themeToEdit = game.themeInfo
    self.showThemeEditor = true
    
}

@State var 不存储值

@State var doesn't store value

swiftui

swiftui-state