我以前用过很多次核心数据，但这让我完全不知所措，这非常令人沮丧。
简而言之，我发出了一个返回12个结果的服务器请求，我可以看到这12个结果被迭代并添加到我的核心数据实体（朋友）中。一旦完成，我对朋友实体中的所有结果发出了一个获取请求，它只返回1个结果，似乎总是最后添加的结果。
我的代码如下。
向服务器发出的请求：

func getFriends(token: String) async throws -> Int {
    var request = EndPoints().getFriendsEndPoint()
    request.httpMethod = "GET"
    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
    let (data, response) = try await URLSession.shared.data(for: request)
    let httpResponse = response as? HTTPURLResponse
    guard (response as? HTTPURLResponse)?.statusCode == 200 else {return httpResponse?.statusCode ?? 0}
    let decodedLocations = try JSONDecoder().decode([FriendsStruct].self, from: data)
    ///Update Locations Core Data record
    self.updateCoreDataFriendsRecords(friendsData: decodedLocations)
    return httpResponse?.statusCode ?? 1000
}

将响应记录保存到Core Data：

func addFriendsDetailsToCoreData(friendsData:[FriendsStruct]) {
    deleteFriendsDetailsData()
    let data = NSEntityDescription.insertNewObject(forEntityName: "Friends", into: self.managedObjectContext) as! Friends
    for items in friendsData {
        data.initials = items.initials
        data.username = items.username
        data.id = items.id
        data.activeEventId = items.activeEventId
        data.email = items.email
        data.firstName = items.firstName
        data.lastName = items.lastName
        data.isInActivity = items.isInActivity
        data.fullName = items.fullName
        print("Adding friend")
    }
    print("saving core data = \(friendsData.count)")
    SaveCoreData().save()
}

最后，从Core Data获取新结果：

let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
var fetchedFriendsResults = [Friends]()

func fetchFriends() -> [Friends] {
    fetchedFriendsResults.removeAll()
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Friends")
    let sortDescriptor = NSSortDescriptor(key: "username", ascending: true)
    fetchRequest.sortDescriptors = [sortDescriptor]
    do {
        if let fetchResults = try managedObjectContext.fetch(fetchRequest) as? [Friends] {
                print("Number of items in friends = \(fetchResults.count)")
                for items in fetchResults {
                    print("A Friend - \(items.fullName ?? "Unknown")")
                fetchedFriendsResults = fetchResults
                return fetchedFriendsResults
            }
        }
    }
    catch {
        return fetchedFriendsResults
    }
    return fetchedFriendsResults
}