长按删除核心数据行

Question

我创建了一个新的带有核心数据的 Mac OS xcode 应用程序，并且正在使用生成的允许您添加项目的默认代码。

但我想改变删除行的方式。使用长按手势触发删除。

查看：

var body: some View {
    List {
        ForEach(items) { item in
            Text("Item at \(item.timestamp!, formatter: itemFormatter)")
                
        }
        //.onDelete(perform: deleteItems) Want to change this command to the one below
          .onLongPressGesture(minimumDuration: 1.5, perform: deleteItems)

    }
    .toolbar {
        Button(action: addItem) {
            Label("Add Item", systemImage: "plus")
        }
    }
}

删除项目功能

private func deleteItems(offsets: IndexSet) {
    withAnimation {
        offsets.map { items[$0] }.forEach(viewContext.delete)

        do {
            try viewContext.save()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            let nsError = error as NSError
            fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
        }
    }

但我收到以下错误

无法将类型 '(IndexSet) -> ()' 的值转换为预期的参数类型 '() -> Void'

Answer 1

“.onDelete（执行操作：（（IndexSet）-> Void）？）”和 “.onLongPressGesture(minimumDuration: Double = 1.5, 执行动作: @escaping () -> Void)” 如您所见，有不同的签名。所以你在做什么是行不通的。

你可以试试这样的：

List {
    ForEach(items, id: \.self) { item in
        Text("Item at \(item)")
            .onLongPressGesture(minimumDuration: 1.5, perform: {deleteItems2(item)})
    }
   // .onDelete(perform: deleteItems)
}
    
private func deleteItems2(_ item: Item) {
    if let ndx = items.firstIndex(of: item) {
        viewContext.delete(items[ndx])
    do {
        try viewContext.save()
    } catch {
        // Replace this implementation with code to handle the error appropriately.
        // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        let nsError = error as NSError
        fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
    }
  }
}