SwiftUI在foreach中是否可以传递绑定范围？

Question

我想在foreach内部的模型中传递一个数组的范围。

我重新创建了一个示例：

import SwiftUI

class TheModel: ObservableObject {
    @Published var list: [Int] = [1,2,3,4,5,6,7,8,9,10]
}

struct MainView: View {
    @StateObject var model = TheModel()
    var body: some View {
        VStack {
            ForEach (0...1, id:\.self) { item in
                SubView(subList: $model.list[0..<5])  <-- error if I put a range                    
            }
        }
    }
}

struct SubView: View {
    @Binding var subList: [Int]
    var body: some View {
        HStack {
            ForEach (subList, id:\.self) { item in
                Text("\(item)")
            }
        }
    }
}

struct MainView_Previews: PreviewProvider {
    static var previews: some View {
        MainView()
    }
}

周围的工作

我发现是传递所有的列表，并在子视图内部执行范围。但我不想这样做,因为数组非常大：

struct MainView: View {
@StateObject var model = TheModel()
var body: some View {
    VStack {
        ForEach (0...1, id:\.self) { i in
            SubView(subList: $model.list, number: i, dimension: 5)
        }
    }
}
}

struct SubView: View {
    @Binding var subList: [Int]
    var number: Int
    var dimension: Int
    
    var body: some View {
        HStack {
            ForEach (subList[number*dimension..<dimension*(number+1)].indices, id:\.self) { idx in
                Button(action: {
                    subList[idx] += 1
                    print(subList)
                }, label: {
                    Text("num: \(subList[idx])")
                })
                
            }
            
        }
    }
}

Answer 1

我会将模型传递给子视图，因为它是一个类，并且将通过引用传递，然后将范围作为单独的参数传递。

这是我对SubView的新实现

struct SubView: View {
    var model: TheModel
    var range: Range<Int>
    var body: some View {
        HStack {
            ForEach (model.list[range].indices, id:\.self) { idx in
                HStack {
                    Button(action: {
                        model.list[idx] += 1
                        print(model.list)
                    }, label: {
                        Text("num: \(model.list[idx])")
                    })
                }
            }
        }
    }
}

注意，我向foreach头添加了indexs以确保使用索引而不是数组中的值访问数组。

调用视图将如下所示

var body: some View {
    VStack {
        SubView(model: model, range: (0..<5))
        Text("\(model.list.map(String.init).joined(separator: "-"))")
    }

额外的文本只是用于测试目的