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

Question

正在开发示例应用程序。目标是从 Master 中的 CoreData 中提取一个列表，然后单击一个以转到详细信息，您可以在其中编辑信息并保存。当您在详细信息中编辑 "name" 时，它不仅会更新详细信息以反映更改，还会反映主文件的更改。我已经尝试了很多方法来实现这个，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

您需要将DetailView中的实体绑定到MasterView传入的实体上。声明为 @Binding var entityName: EntityName

Answer 2

正如所承诺的那样，这里是一个 link 示例使用 CoreData 的 SwiftUI 程序。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。我写了一个 CoreDataDataSource class，它做的事情基本上是一样的，而且还有更多。

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

Answer 3

正如@trapper 所解释的那样，entityName 必须绑定到 MasterView。

当您在 DetailView 中添加 @ObservedObject 时，更新会反映如下：

@ObservedObject var entityName:EntityName

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

SwiftUI / CoreData / Master / Detail (with editing) / Xcode 11 - Beta 5

core-data

swiftui

xcode11