Question

我的应用程序中有这个数据结构。如您所见，我认为每个汽车品牌都由一个经销商销售，而经销商可能会销售多个品牌。

我从网络服务中检索CarBrand数据。由于我批量获取数据，如何保存数据，以便将carbrand数据与Delear记录相关联（从而保持我建立的关系）

这是我的尝试：

        let moc = DataController().managedObjectContext

        let carbrandEntity = NSEntityDescription.insertNewObjectForEntityForName("carbrandEntity", inManagedObjectContext: moc) as! CarBrand

        let dealerEntity = NSEntityDescription.insertNewObjectForEntityForName("DealerEntity", inManagedObjectContext: moc) as! Dealer

        for carbrand in self.carbrandArray {
            // add our data
            carbrandEntity.setValue(carbrand[0], forKey: "brandname")
            carbrandEntity.setValue(carbrand[1], forKey: "makeyear")

            do {
                try moc.save()
            } catch {
                fatalError("Failure to save context: \(error)")
            }

        }

        dealerEntity.setValue("Steven&Sons", forKey: "name")
        // How do I save dealer entity so that it is associated with the carbrand data that I just added.

更新

这是我的尝试，但是当我拿到特定的经销商时，我得到经销商信息，但CarBrand（NSSet）总是空的。

        let moc = DataController().managedObjectContext

        let carbrandEntity = NSEntityDescription.insertNewObjectForEntityForName("carbrandEntity", inManagedObjectContext: moc) as! CarBrand

        let dealerEntity = NSEntityDescription.insertNewObjectForEntityForName("DealerEntity", inManagedObjectContext: moc) as! Dealer

        dealerEntity.setValue("Steven&Sons", forKey: "name")

        for carbrand in self.carbrandArray {
            // add our data
            carbrandEntity.setValue(carbrand[0], forKey: "brandname")
            carbrandEntity.setValue(carbrand[1], forKey: "makeyear")


        }

        do {
                try moc.save()
        } catch {
                fatalError("Failure to save context: \(error)")
        }

更新

我还没有收到任何carband数据。这是一个更新的代码

        let dealerEntity = NSEntityDescription.insertNewObjectForEntityForName("DealerEntity", inManagedObjectContext: moc) as! Dealer

        dealerEntity.setValue("Steven&Sons", forKey: "name")

        for c in self.carbrandArray {
            dealerEntity.carbrand?.setValue(c[0], forKey: "brandname")
            dealerEntity.carbrand?.setValue(c[1], forKey: "makeyear")

        }

如果我在提取时犯了任何错误，请查看我的FETCH代码

        let moc = DataController().managedObjectContext
        let dealerEntity = NSFetchRequest(entityName: "DealerEntity")

        do {
            let dealers = try moc.executeFetchRequest(dealerEntity) as! [Dealer]
            for d in dealers {
               print(d.carbrand!.count) // Returns 0
            }

        } catch {
           fatalError("Failed to fetch saved data: \(error)")
    }

Answer 1

所以我简化了一个示例供您查看。我在这里上传了一个项目文件，对我来说很有效。

project file

我并不是说这是一个完美的解决方案，也不是我声称这些是最佳做法。我只是向您展示这个概念以及我如何处理这个问题。

这是我的数据模型的样子。

这是完成任务的代码。请注意，我们正在封装将对象存储在Managed Object类本身中所必需的逻辑。这不是一项要求，但它是我用来保持代码清洁的一种方法。

发表

public final class Post: NSManagedObject { @NSManaged var title: String @NSManaged var body: String @NSManaged var date: NSDate? @NSManaged var comments: Set<Comment>? // Insert code here to add functionality to your managed object subclass public static func insertIntoContext(moc: NSManagedObjectContext, json: AnyObject) { print("\n==============\n Post: \n\(json) \n==============\n") let post = NSEntityDescription.insertNewObjectForEntityForName("Post", inManagedObjectContext: moc) as! Post guard let title = json["title"] as? String, body = json["body"] as? String else { assertionFailure("post body failed"); return } post.title = title post.body = body post.date = NSDate() if let jsonComments = json["comments"] as? [AnyObject] { // pass comments data into our comments class to get inserted into // our context let comments = Comment.returnSet(moc, jsonArray: jsonComments) post.comments = comments } do { try moc.save() } catch let error { print("failed: \n\(error)\n\n<- - - - ->") } } }

<强>注释

public final class Comment: NSManagedObject { @NSManaged var text: String @NSManaged var name: String public static func returnSet(moc: NSManagedObjectContext, jsonArray: [AnyObject]) -> Set<Comment> { var comments = Set<Comment>() for answer in jsonArray { // this guard statement will continue to the next object if our insert fails guard let c = Comment.insertIntoContext(moc, json: answer) else { continue } comments.insert(c) } return comments } public static func insertIntoContext(moc: NSManagedObjectContext, json: AnyObject) -> Comment? { //print("\ncomment : \n \(json)\n") guard let jsonText = json["text"] as? String, jsonName = json["name"] as? String else { assertionFailure("");return nil } let comment = NSEntityDescription.insertNewObjectForEntityForName("Comment", inManagedObjectContext: moc) as! Comment comment.text = jsonText comment.name = jsonName return comment } }

<强>的ViewController

class ViewController: UIViewController { var moc: NSManagedObjectContext! override func viewDidLoad() { super.viewDidLoad() // you'd get your data from a webserver ideally let postObj : [String: AnyObject] = [ "title" : "some title", "body" : "this is some body text", "comments" : [ [ "text":"some comment", "name":"dan beaulieu" ], [ "text":"another comment comment", "name":"user30646" ], [ "text":"a much wiser comment", "name":"Rob" ] ] ] // then you pass in your object and your context Post.insertIntoContext(moc, json: postObj) let posts = NSFetchRequest(entityName: "Post") do { let posts = try moc.executeFetchRequest(posts) as! [Post] for p in posts { print("------- Comments ------") print(p.comments) // Returns 0 } } catch { fatalError("Failed to fetch saved data: \(error)") } } }

<强>的AppDelegate

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool { // Override point for customization after application launch. guard let vc = window?.rootViewController as? ViewController else { fatalError("Wrong View Controller Type") } vc.moc = managedObjectContext return true }

如何保存关系数据（核心数据）

1 个答案: