Question

在以下代码中滑动删除SubView1中的一行时出现错误。

class Model: ObservableObject {
    @Published var items: [Item]
    
    init(name: String, items: [Item]) {
        self.items = items
    }
    
    func delete(at offsets: IndexSet) {
        self.items.remove(atOffsets: offsets)
    }
}

class Item: Identifiable, ObservableObject, Equatable {
    static func == (lhs: Item, rhs: Item) -> Bool {
        return lhs.id == rhs.id
    }
    
    var id = UUID()
    var itemName: String
    @Published var subItems: [SubItem]
    
    init(itemName: String, payments: [SubItem]) {
        self.itemName = itemName
        self.subItems = payments
    }
    
    func delete(at offsets: IndexSet) {
        self.subItems.remove(atOffsets: offsets)
    }
}

class SubItem: Identifiable, ObservableObject, Equatable {
    static func == (lhs: SubItem, rhs: SubItem) -> Bool {
        return lhs.id == rhs.id
    }
    
    var id = UUID()
    var isOn: Bool
    
    init(isOn: Bool) {
        self.isOn = isOn
    }
}


struct MainView: View {
    @EnvironmentObject var model: Model
    
    var body: some View {
        NavigationView {
            List {
                ForEach(model.items) {item in
                    NavigationLink(destination: SubView1(item: self.$model.items[self.model.items.firstIndex(of: item) ?? 0])) {
                        HStack{
                            Text(item.itemName)
                            ForEach(item.subItems) {subItem in
                                Text(subItem.isOn ? "True": "False")
                            }
                        }
                    }
                }.onDelete(perform: model.delete)
            }
        }
    }

}
// Here ------>
struct SubView1: View {
    @Binding var item: Item
    var body: some View {
        List {
            ForEach(0..<item.subItems.count) {index in
                NavigationLink(destination: SubView2(subItem: self.$item.subItems[index])) {
                    ToggleView(subItem: self.$item.subItems[index])
                }
                
            }.onDelete(perform: item.delete)
        }
    }
}

struct SubView2: View {
    @Binding var subItem: SubItem
    var body: some View {
        Toggle(isOn: $subItem.isOn) {
            Text("Toggle-Text")
        }
    }
}


struct ToggleView: View {
    @Binding var subItem: SubItem
    var body: some View {
        Toggle(isOn: $subItem.isOn) {
            Text("Toggle-Text")
        }
    }
}

错误是：

Thread 1: Fatal error: Index out of range

我还尝试了SubView1的另一个代码：

struct SubView1: View {
    @Binding var item: Item
    var body: some View {
        List {
            ForEach(item.subItems) {subItem in
                NavigationLink(destination: SubView2(subItem: self.$item.subItems[self.item.subItems.firstIndex(of: subItem) ?? 0])) {
                    ToggleView(subItem: self.$item.subItems[self.item.subItems.firstIndex(of: subItem) ?? 0])
                }
                
            }.onDelete(perform: item.delete)
        }
    }
}

这是为什么？

Answer 1

可悲的是，您的代码无法编译，我不觉得自己在寻找错误。 ->提供一个编译并运行的示例，以便我们实际上可以尝试解决问题，而不必首先解决编译问题。 How to create a Minimal, Reproducible Example

通常，我建议您不要对带有空白索引的数组执行操作。特别是您知道的那些在运行时会被修改。至少在执行操作之前对其进行测试。仅在数组为最终数组时才使用直接索引，否则进入索引超出范围的风险就太高了。

对于您的onDelete，请尝试使用这种方法：

List {
    ForEach(listItems, id: \.self) { (item) in
        Text(item)
    }.onDelete { (indexSet) in
        self.listItems.remove(atOffsets: indexSet)
    }
}

有关此内容的更多信息：Delete List item with SwiftUI

要对不安全的索引不执行操作，请尝试以下操作：

if let index = self.myData.firstIndex(of: self.item) {
       self.myData.remove(at: index)
}

有关此内容的更多信息： Removing from array - Fatal error: Index out of range - SwiftUI Binding

SwiftUI线程1：致命错误：索引超出范围

1 个答案: