SwiftUI & CoreData:如何计算“真”布尔值的数量并在VGrid中显示结果

import SwiftUI
import CoreData

struct ContentView: View {
    @Environment(\.managedObjectContext) private var viewContext
    
    @FetchRequest(
        sortDescriptors: [],
        animation: .default)
    private var items: FetchedResults<Item>
    
    var body: some View {
        VStack {
            Text("真布尔值的数量：\(trueCount)")
            
            VGrid(items, columns: [GridItem(.flexible()), GridItem(.flexible())]) { item in
                Text(item.name ?? "")
            }
        }
    }
    
    private var trueCount: Int {
        items.filter { $0.isTrue }.count
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
    }
}