SwiftUI / CoreData / Master / Detail（带编辑）/ Xcode 11 - Beta 5

Question

处理示例应用程序。目标是从 Master 中的 CoreData 中提取一个列表，然后单击一个列表以转到详细信息，您可以在其中编辑信息并保存。当您在细节中编辑“名称”时，它不仅会更新细节以反映更改，而且还会反映母版上的更改。我已经尝试了很多方法来实现这一点，但到目前为止还没有找到答案。

// Code generation is turned OFF in the xcdatamodeld file

public class EntityName: NSManagedObject, Identifiable {
   @NSManaged public var name: String
   @NSManaged public var active: Bool
}

extension EntityName {
    static func allEntityNameFetchRequest() -> NSFetchRequest<EntityName> {
        let request: NSFetchRequest<EntityName> = EntityName.fetchRequest() as! NSFetchRequest<EntityName>
        request.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
        return request
   }
}


struct MasterView: View {

    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(fetchRequest: EntityName.allEntityNameFetchRequest()) var allEntityNames: FetchedResults<EntityName>


    var body: some View {
        NavigationView {
            List {
                ForEach(self.allEntityNames) { entityName in
                NavigationLink(destination: DetailView(entityName: entityName)) {
                    VStack(alignment: .leading) {
                        Text(entityName.name)
                            .font(.headline)
                        Text(String(entityName.active))
                            .font(.subheadline)
                    }
                }
            }
        }
    }
    .onAppear() {
        // Just want to populate the Core Data to have a few to work with
        if self.allEntityNames.count == 0 {
            for _ in 1...3 {
                let newEntry = EntityName(context: self.managedObjectContext)
                newEntry.name = "New Entry"

                try! self.managedObjectContext.save()
            }
         }
      }
   }
}

struct DetailView: View {

   var entityName = EntityName()

   var body: some View {
       VStack {
           Text("Name: \(entityName.name)")
           Text("Active: \(String(entityName.active))")

           // What I'd like to do now:
              //TextField("", text: $entityName.name)
              //Toggle(isOn: $entityName.active)
       }
   }
}

Answer 1

正如所承诺的，这里是使用 CoreData 的示例 SwiftUI 程序的链接。当前版本在 GM 版本上编译和运行。它不使用新的 @FetchRequest 属性包装器，因为它不能满足我的所有需求。我编写了一个 CoreDataDataSource 类，它基本上执行相同的操作，并且还执行更多操作。

https://github.com/Whiffer/SwiftUI-Core-Data-Test