如何解决创建新应用时,如何停止CoreData产生样板代码?
新开发者问题
在Xcode中,当创建一个包含CoreData的新应用程序时,它会生成样板代码,该代码来自我从在线教程课程中下载的基本“提醒”应用程序。如何使Xcode恢复为默认配置?
我创建了6个具有不同配置的应用程序,并且仅在包含CoreData时才生成。 我包括了UI预览的屏幕截图。模拟器为空。
这是 ContentView.swift
中的代码import SwiftUI
import CoreData
struct ContentView: View {
@Environment(\.managedobjectContext) private var viewContext
@FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp,ascending: true)],animation: .default)
private var items: FetchedResults<Item>
var body: some View {
List {
ForEach(items) { item in
Text("Item at \(item.timestamp!,formatter: itemFormatter)")
}
.onDelete(perform: deleteItems)
}
.toolbar {
#if os(iOS)
EditButton()
#endif
Button(action: addItem) {
Label("Add Item",systemImage: "plus")
}
}
}
private func addItem() {
withAnimation {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
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)")
}
}
}
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,\(nsError.userInfo)")
}
}
}
}
private let itemFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .short
formatter.timeStyle = .medium
return formatter
}()
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView().environment(\.managedobjectContext,PersistenceController.preview.container.viewContext)
}
}
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