有一个名为 Item 的实体,它有一个名为 amount 的 Double 属性,向你的 View 添加一个计算属性:
Code:
swift
struct ContentView: View {
@Environment(\.managedObjectContext) private var viewContext
@FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)],
animation: .default)
private var items: FetchedResults<Item>
var totalAmount: Double {
items.reduce(0) { $0 + $1.amount }
}
var body: some View {
List {
ForEach(items) { item in
HStack {
Text("Item \(item.name!)")
Spacer()
Text("\(item.amount)")
}
}
Divider()
Text("Total Amount: \(totalAmount)")
}
}
}