SwiftUI List -> ForEach -> Item 是一个让，所以我不能改变一个值

Posted 2023-02-24

【中文标题】SwiftUI List -> ForEach -> Item 是一个让，所以我不能改变一个值

【英文标题】：SwiftUI List -> ForEach -> Item is a let, so i can't change a value

【发布时间】：2021-05-16 09:39:00

【问题描述】：

如果我点击列表中的一个项目（只需切换它），我想更改“点击”的值...... 但是这个错误来了：“不能在不可变值上使用变异成员：'item'是'let'常量” 我理解它是正确的，但我不知道如何修复那个“项目”，不再允许 即使我在结构中创建一个变异函数来更改值也不起作用

感谢您的帮助！

struct Gamemode: Identifiable 
    var id: Int
    var name: String
    var clicked: Bool


struct ContentView: View 
    
    @State private var gamemodes: [Gamemode] = [
        Gamemode(id: 1, name: "example text", clicked: false),
        Gamemode(id: 2, name: "second example text", clicked: false),
        Gamemode(id: 3, name: "third example text", clicked: false),
        Gamemode(id: 4, name: "fourth example text", clicked: false)
    ]
    
    
    
    var body: some View 
        List 
            ForEach(gamemodes)  item in
                    VStack 
                        Text("Selection \(item.id)")
                        Text("\(item.name)")
                    
                    .background(Color((item.clicked) ? .blue : .yellow))
                    .onTapGesture 
                        item.clicked.toggle()
                    
            
        
    

【参考方案1】：

我不知道这是否是最好的解决方案，但也许是这样：

import SwiftUI

struct Gamemode: Identifiable 
    var id: Int
    var name: String
    var clicked: Bool


struct ContentView: View 

    @State private var gamemodes: [Gamemode] = [
        Gamemode(id: 1, name: "example text", clicked: false),
        Gamemode(id: 2, name: "second example text", clicked: false),
        Gamemode(id: 3, name: "third example text", clicked: false),
        Gamemode(id: 4, name: "fourth example text", clicked: false)
    ]



    var body: some View 
        List 
            ForEach(0..<gamemodes.count)  index in
                    VStack 
                        Text("Selection \(gamemodes[index].id)")
                        Text("\(gamemodes[index].name)")
                    
                    .background(Color((gamemodes[index].clicked) ? .blue : .yellow))
                    .onTapGesture 
                        gamemodes[index].clicked.toggle()