Swift 3：如何在按下 UI 按钮时删除 Core Data 中的单个记录

Question

我有一个功能，我可以将配置文件添加到收藏夹列表（通过核心数据保存），当我想将其标记为“不喜欢”时，它应该从核心数据和表列表视图（收藏夹视图控制器）中删除）。

到目前为止，我拥有的代码从列表中删除所有记录，而不是删除特定记录。

请在下面找到代码：-

 @IBAction func saveFav(_ sender: UIButton) {

   let propertyToCheck = sender.currentTitle!
    var proID = saved_id
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let task = FavProfile(context: context)

    switch propertyToCheck {
    case "Add to Favourite":
     // Link Task & Context
    task.busName = bussinessName
    task.profileID = Int32(id!)!
    print ("saved id is: - \(task.profileID)")
    print ("saved profile name is: - \(task.busName)")
    fav_remove_fav_button_label.setTitle("Remove From Favourite", for: .normal)

    // Save the data to coredata
    (UIApplication.shared.delegate as! AppDelegate).saveContext()

    let _ = navigationController?.popViewController(animated: true)

    let alert = UIAlertController(title: "Alert", message: "Added to your Favourite list", preferredStyle: UIAlertControllerStyle.alert)
    alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
    self.present(alert, animated: true, completion: nil)

        case "Remove from Favourite":



            let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "FavProfile")
            let moc = getContext()
            let result = try? moc.fetch(fetchRequest)
            let resultData = result as! [FavProfile]

            for object in resultData {
                moc.delete(object)
            }

            do {
                try moc.save()
                print("saved!")
            } catch let error as NSError  {
                print("Could not save \(error), \(error.userInfo)")
            } catch {

            }




        let alert = UIAlertController(title: "Alert", message: "Removed from your Favourite list", preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
        self.present(alert, animated: true, completion: nil)
      //  self.favtable.tableView.reloadData()


    default: break
    }
}

我不知道我需要在这里修复什么，只删除特定的记录。

感谢您的时间和努力。

屏幕 1，当我将个人资料标记为收藏时：

当我将相同的个人资料标记为不喜欢时的屏幕 2：

屏幕 3，当我再次重新启动应用程序时：

我试图将第二个配置文件标记为不喜欢，它不会更新 tableview。 当我重新启动应用程序时，它显示“标签”

Answer 1

    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "FavProfile")
    let predicate = NSPredicate(format: "profileID == %@", id as CVarArg)
    fetchRequest.predicate = predicate
    let moc = getContext()
    let result = try? moc.fetch(fetchRequest)
    let resultData = result as! [FavProfile]

    for object in resultData {
        moc.delete(object)
    }

    do {
        try moc.save()
        print("saved!")
    } catch let error as NSError  {
        print("Could not save \(error), \(error.userInfo)")
    }

对 profileID 使用谓词。

Answer 2

let predicate = NSPredicate(format: "name == %@ AND type == %@", "your target name","your target type")
            var fetchedEntities = [TrackTable]()
            let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "TrackTable")
            fetchRequest.predicate = predicate
            do {
                    fetchedEntities = try! managedContext?.fetch(fetchRequest) as! [TrackTable]
                    for sequence in fetchedEntities
                    {
                        managedContext?.delete(sequence)
                    }
                    catch
                    {

                    }
     }

在上面的谓词name和type是您要删除特定实体的表实体。

Answer 3

* Add a Predicate Like given below to search for a particular item from the list of Favourites using it's unique profile Id. Search for that item in it's entity and delete that item from core data.
*****************************************
let predicateFavs = NSPredicate(format: “profileID = %@", String(describing: id!))
    let favList = CoreDataHandler.sharedInstance.fetchEntityWithName(“FavProfile”, predicate: predicateFavs) as! [FavProfile]

    context.performAndWait({
    for object in favList{
    self.context.delete(object)
    }

    do {
    try self.context.save()

    } catch {
    print("error : \(error)")
    }
    })


********************************************   



    func fetchEntityWithName(_ entityName : NSString, predicate: NSPredicate) -> NSArray{

        // Create Entity Description
        let entityDescription = NSEntityDescription.entity(forEntityName: entityName as String, in: context)
        // Initialize Fetch Request
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>()
        // Configure Fetch Request
        fetchRequest.entity = entityDescription
        fetchRequest.predicate = predicate
        var result = NSArray()
        do {
            result = try context.fetch(fetchRequest) as NSArray
            print(result)

        } catch {
            let fetchError = error as NSError
            print(fetchError)
        }

        return result
    }