Question

Swift编程新手，并且在使用Core Data时出现问题。我试图删除通过Int64号码链接到主实体的2个其他实体中的条目。

GameInfo - 主实体。有比赛号码，球队名称，得分，日期属性等。 HomeSubstitution＆amp; AwaySubstitution-两队换人。每场比赛可以超过一场。将游戏编号作为每个记录集中的属性。

我与实体建立了关系并制作了删除规则= Cascade。

我可以删除删除GameInfo记录集但它已经消失，但HomeSubstitution和AwaySubstitution记录仍然存在。当您开始新游戏时，旧数据现在链接到新游戏。即，继续查看游戏，并使用新游戏显示已删除的GameInfo中的替换。

这是我的代码。

@objc lazy var fetchedResultsController: NSFetchedResultsController<GameInfo> = {
    let fetchRequest: NSFetchRequest<GameInfo> = GameInfo.fetchRequestGame()
    fetchRequest.sortDescriptors = [NSSortDescriptor(key: "gameNumber", ascending: true)]
    let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
    fetchedResultsController.delegate = self

    return fetchedResultsController
}()

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {
        // Fetch game
        let gameRow = fetchedResultsController.object(at: indexPath)
        let gameNumberDelete = gameRow.gameNumber
        print("game row to delete: \(gameRow)")
        print("game number to delete: \(String(describing: gameNumberDelete))") //This works and I get the game number
        // Delete game
        gameRow.managedObjectContext?.delete(gameRow)
    }
}

我尝试使用类似的代码来执行fetchedHomeController和fetchedAwayController，这些代码引用了引用不同实体的fetchedResultsController和NSPredicate（在其他类中用于查看游戏），但是我得到了错误。

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {
        // Fetch game
        let gameRow = fetchedResultsController.object(at: indexPath)
        let gameNumberDelete = gameRow.gameNumber
        print("game row to delete: \(gameRow)")
        print("game number to delete: \(String(describing: gameNumberDelete))")
        // Delete game
        gameRow.managedObjectContext?.delete(gameRow)
        //Delete home substitutions
        let fetchRequestHome = NSFetchRequest<NSFetchRequestResult>(entityName: "HomeSubstitution")
        fetchRequestHome.predicate = NSPredicate(format: "homeGameLink == %i", gameNumberDelete)
        fetchRequestHome.returnsObjectsAsFaults = false

        print("fetchRequestHome: \(fetchRequestHome)")

        do {
            try self.fetchedHomeController.performFetch()
            let homeGameDelete = fetchedHomeController.object(at: indexPath)
            print("homeGameDelete: \(homeGameDelete)")
            homeGameDelete.managedObjectContext?.delete(homeGameDelete) //Error here to do with NSFetchedResultsController.
        } catch {
            let fetchError = error as NSError
            print("Unable to Perform Fetch Request")
            print("\(fetchError), \(fetchError.localizedDescription)")
        }
    }
}

我怀疑删除次数超过我选择的行数且NSFetchedResultsController不允许这样做。

编辑：弄清楚了。使用Raj Joshi在Delete Object from Core Data中给出的例子。

 func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {
        // Fetch game
        let mocGame = getContext()
        let gameRow = fetchedResultsController.object(at: indexPath)
        let gameNumberDelete = gameRow.gameNumber
        print("game row to delete: \(gameRow)")
        print("game number to delete: \(String(describing: gameNumberDelete))")
        // Delete game
        gameRow.managedObjectContext?.delete(gameRow)
        do {
            try mocGame.save()
            print("saved Game Deletion!")
        } catch let error as NSError  {
            print("Could not save \(error), \(error.userInfo)")
        } catch {

        }
        //Delete substitutions based on gameNumber
        deleteHomeGameData(link: gameNumberDelete)
        deleteAwayGameData(link: gameNumberDelete)

    }
}

func deleteHomeGameData(link: Int64) -> Void{

    let mocHome = getContext()
    let fetchRequestHome = NSFetchRequest<NSFetchRequestResult>(entityName: "HomeSubstitution")
    fetchRequestHome.predicate = NSPredicate(format: "homeGameLink == %i", link)

    do {
        let result = try? mocHome.fetch(fetchRequestHome)
        let resultData = result as! [HomeSubstitution]

        //Loop through substitutions and delete.
        for object in resultData {
            mocHome.delete(object)
        }

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

        }
    }
}

func deleteAwayGameData(link: Int64) -> Void{

    let mocAway = getContext()
    let fetchRequestAway = NSFetchRequest<NSFetchRequestResult>(entityName: "AwaySubstitution")
    fetchRequestAway.predicate = NSPredicate(format: "awayGameLink == %i", link)

    do {
        let result = try? mocAway.fetch(fetchRequestAway)
        let resultData = result as! [AwaySubstitution]

        //Loop through substitutions and delete.
        for object in resultData {
            mocAway.delete(object)
        }

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

        }
    }
}

func getContext () -> NSManagedObjectContext {
    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    return appDelegate.persistentContainer.viewContext
}

删除多个实体中的核心数据条目

0 个答案: