无法调整已删除的类别总数

Question

我有一个用户可以创建和删除的 5 个费用类别的列表。删除用户类别时，我需要从总计和所有用户类别的总计中减去类别总计。此外，删除类别之后的任何用户类别都必须将总数在 totalArray 中向下移动一个位置。在 C 中，这将是一个简单的操作，但在 SwiftUI 中，我不知道从哪里开始。我可以使用索引来判断我要删除的类别吗？

错误包括“无法将 'IndexSet.type' 类型的值转换为预期的参数类型 'Int'”，以及“'Int' 类型的表达式模式无法匹配 'IndexSet' 类型的值]

假设我定义了所有 5 个类别。如果我删除类别 #2，我需要将类别 3 - 5 的总数向下移动一位到 2 - 4 的总数。显示用户类别总计时，categories.catItem.count用于检查每个类别总计（第一、二、三类等）的有效性。

// this definition is found in different file (Class UserData)
@Published var totalArray = [Double] ()


         ...


struct manCatView: View {
    
    @EnvironmentObject var userData: UserData
    @EnvironmentObject var categories: Categories
    
    var body: some View {

 List {
            ForEach(categories.catItem) { item in
                if item.noShow == false {
                    
                    HStack {
                        Image(systemName: item.catPix).resizable()
                           .frame(width: 30, height: 30)
                       
                       Spacer() 

                       Text(item.catName)
                    }
                }
            }
            .onDelete(perform: removeItems)
        }
        .navigationBarTitle(Text("Manage Categories"), displayMode: .inline)


         ...

func removeItems（偏移量：IndexSet）{

        // at this point the deleted category still exists
   
        // 1. must subtract 'to be deleted' category total from userTotal and grandTotal
            if userData.totalArray[IndexSet] != 0 {
                userData.totalArray[grandTotal] -= userData.totalArray[IndexSet]
                userData.totalArray[userTotal] -= userData.totalArray[IndexSet]
        }
        
        // 2. must shift up category totals following the deleted category
        switch offsets
        {
        
        case 0:    // 1st category being deleted
        
        case 1:    // 2nd category being deleted
        
        case 2:    // 3rd category being deleted      
              
        case 3:    // 4th category being deleted
            
        case 4:    // 5th category being deleted

        default:
        }

        // 3. delete category
    categories.catItem.remove(atOffsets: offsets)
}

Answer 1

我不确定这是否更好。我将类别总计移到了存储结构中。除了删除类别外，还需要先调整合计。当用户单击删除时，removeItems 函数指针指向要删除的类别。您可能认为获取类别总数 (categories.catItem[].catTotal) 很容易，但我收到错误“无法将类型 'IndexSet' 的值转换为预期的参数类型 Int”。我认为 Asperi 希望我尝试某种映射，但我不确定从哪里开始。

struct CatItem:  Codable, Identifiable {
        var id = UUID()
        var catNum: Int         // entryView category pointer
        var catName: String     // category name
        var catTotal: Double    // category total
        var catPix: String      // sf symbol
        var catShow: Bool       // don't show certain categories
    }
    
   
     class Categories: ObservableObject {
            
            @Published var catItem: [CatItem] {
            }
        }



    ...





struct manCatView: View {
    
    @EnvironmentObject var userData: UserData
    @EnvironmentObject var categories: Categories

    var pic: String = ""

    var body: some View {
       List {
         ForEach(categories.catItem) { index in
             if index.catShow == true {  
                 HStack {
                      let pic = categories.catItem[index].catPix
                      Image(systemName: pic)
                          .resizable()
                          .foregroundColor(Color(colors[index]))
                          .frame(width: 40, height: 40)
                        
                       Text("")
                           .frame(width: 40, alignment: .leading)
                        
                       Text(index.catName)
                    }
                }
            } // end foreach
            .onDelete(perform: removeItems)
            
        } // end list
        .navigationBarTitle(Text("Manage Categories"), displayMode: .inline)
   }

   func removeItems(at offsets: IndexSet) {
        
        //subtract category amount from system totals. 
        let catTotal = categories.catItem[offsets].catTotal  // <-- error here
        userData.totalArray[grandTotal] -= catTotal
        userData.totalArray[userTotal] -= catTotal
        
        categories.catItem.remove(atOffsets: offsets)
    }
}

无法调整已删除的类别总数

Unable to Adjust Deleted Category Totals

swiftui

ios14