ForEach 中的自定义状态绑定答案

【问题标题】：Custom Binding of State inside ForEachForEach 中的自定义状态绑定
【发布时间】：2021-06-24 02:45:07
【问题描述】：

我想在我的 Struct 类型的 State 变量中切换变量，但不知道如何构造一个自定义 Binding 到 State 的变量。 Xcode 抛出错误“Cannot assign to property: 'translations' is a 'let' constant”

带有自定义绑定的 ForEach（不起作用）

ForEach(data.translations, id: \.self) { translations in
    
    let binding = Binding(
        get: { translations.target},
        set: { translations.target = $0 }
    )
    
    HStack {
        Text("\(translations.language)")
        Spacer()
        Toggle(isOn: binding) {
            Text("")
        }
        .toggleStyle(CheckboxToggleStyle())
    }
    
}

结构

struct Data: Hashable {
    
    var base: String
    var target: String
    var translations: [Translations]
    
    struct Translations: Hashable {
        let language: String
        var target: Bool
        var texts: [String: Text]
    }
    
    struct Text: Hashable {
        var translation: String
        var pinned: Bool
        var order: Int
    }
    
}

国家

@State var data = Data(
    base: "",
    target: "",
    translations: [ // ADD ALL LANGUAGES. CHECK REMINDERS-APP FOR NOTE ABOUT LANGUAGES
        Data.Translations(
            language: "Danish",
            target: false,
            texts: [
                "..." : Data.Text(translation: "...", pinned: false, order: 0)
            ]
        ),
        Data.Translations(
            language: "Swedish",
            target: true,
            texts: [
                "..." : Data.Text(translation: "...", pinned: false, order: 0)
            ]
        ),
        Data.Translations(
            language: "English",
            target: true,
            texts: [
                "..." : Data.Text(translation: "...", pinned: false, order: 0)
            ]
        )
    ]
)

【问题讨论】：

标签： swift swiftui

【解决方案1】：

您遇到了多个问题，例如命名和尝试更改 ForEach 的 let 项目，这里是救命稻草：

struct DataStruct: Hashable {
    
    var base: String
    var target: String
    var translations: [TranslationsStruct]
    
}

struct TranslationsStruct: Hashable {
    
    let language: String
    var target: Bool
    var texts: [String: TextStruct]
    
}

struct TextStruct: Hashable {
    
    var translation: String
    var pinned: Bool
    var order: Int
    
}

var dataStructInitializing = DataStruct(
    base: "",
    target: "",
    translations: [
        TranslationsStruct(
            language: "Danish",
            target: false,
            texts: [
                "..." : TextStruct(translation: "...", pinned: false, order: 0)
            ]
        ),
        TranslationsStruct(
            language: "Swedish",
            target: true,
            texts: [
                "..." : TextStruct(translation: "...", pinned: false, order: 0)
            ]
        ),
        TranslationsStruct(
            language: "English",
            target: true,
            texts: [
                "..." : TextStruct(translation: "...", pinned: false, order: 0)
            ]
        )
    ]
)

import SwiftUI

struct ContentView: View {
    
    @State private var dataStruct: DataStruct = dataStructInitializing
    
    var body: some View {
        
        VStack {
            
            ForEach(dataStruct.translations.indices, id: \.self) { index in
                
                let binding = Binding(
                    get: { dataStruct.translations[index].target },
                    set: { dataStruct.translations[index].target = $0 }
                )

                Toggle(isOn: binding) { Text(dataStruct.translations[index].language) }

            }
            
        }
        .padding()
        
    }
}

【讨论】：

【解决方案2】：

struct ContentView: View {
    @State private var dataStruct: DataStruct = dataStructInitializing
    var body: some View {
        VStack {
            ForEach($dataStruct.translations, id: \.self) { $translation in
                Toggle(isOn: $translation.target) { Text(translation.language) }
            }
        }
        .padding()
    }
}

另外，制作translations Identifiable 并使用他们的.id 代替.self 也是一个好主意。

【讨论】：