Swift - 如何保存对 CoreData 属性的更改

问题描述

我可以在 CoreData 中保存对象。我的实体属性是字符串类型，并保存输入到文本字段中的任何内容。我可以使用我指定的任何索引的 FetchedEntityRequest[index] 更新属性，但我无法保存传递到 DeatailView 的选定属性。请参阅下面的示例代码。

//save Attribute
    func saveButtonTapped(text: String?) {
        if let context = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer.viewContext {
            let Entity.attribute: String = Entity(context: context)
            Entity.attribute: = text
            if context.hasChanges {
                do {
                    try context.save()
                } catch {
                    print(error.localizedDescription)
                }
            }

 // pass attribute to DetailView from List View
@Environment(\.managedobjectContext) var managedobjectContext
@FetchRequest(
entity: Entity.entity(),sortDescriptors: [
NSSortDescriptor(keyPath: \Entity.attribute,ascending: true)
]
) var fetchedEntityRequest: FetchedResults<Entity>
var body: some View {
    NavigationView {
        List {
            ForEach(fetchedEntityRequest,id: \.self) { entity in
                vstack {
                    HStack {
                    
                    Text(entity.attribute ?? "")
                        .font(.headline)
                    Spacer()
                    NavigationLink(destination: EditLyricsView(text: entity.attribute ?? "")) {
                    }
                }
                .frame(maxWidth: .infinity,maxHeight: .infinity,alignment: .center)
            
        

        //DetailView - updating the index specified and saving changes to coredata.
    

@State var text: String = ""
        @Environment(\.managedobjectContext) var managedobjectContext
        @FetchRequest(
            entity: Entity.entity(),sortDescriptors: [
                NSSortDescriptor(keyPath: \Entity.attribute,ascending: true)
            ]
        ) var fetchedEntityRequest: FetchedResults<Entity>
        var body: some View {
            NavigationView {
                vstack {
                    TextView(text: $text)
                }  .navigationBarTitle(Text("self.text"),displayMode: .inline)
                .navigationBarItems(leading: Button("Home") {
                    presentationMode.wrappedValue.dismiss()
                    
                },trailing: Button("Save") {
                    fetchedEntityRequest.forEach { i in
                        var index: Int = 0
                        fetchedEntityRequest[index].setValue(text,forKey: "Entity.attribute")
                        presentationMode.wrappedValue.dismiss()
                    }
                }
            }
 

解决方法

谢谢阿斯佩里！ - 那行得通。请参阅下面的更新。

NavigationLink(destination: DetailedView(text: entity.attribute ?? "",entity: Entity)) {
}

我在 Entity 类型的 DetailsView 上创建了一个 @Stated var？并调用下面的。

Entity?.setValue(text,forKey: entity.attribute)