领域 - 删除后无法使用 object

Question

我的应用程序中有一个视频播放器。 collection 视图中有一个视频列表。如果您点击其中一个单元格，则会出现一个新的视图控制器来播放所选视频。此外，您可以在这个新视图控制器中循环浏览 collection 视图中的所有视频，因为整个列表都已传递。

问题是：当用户在 PlayerVC 中时，他们可以取消收藏 Video。如果他们这样做，我会从 Realm 中删除 Video object。但是，这会导致：

Terminating app due to uncaught exception 'RLMException', reason: 'Object has been deleted or invalidated.'

基本上，如果用户正在 PlayerVC 观看视频并且他取消了对视频的收藏，我希望他们仍然能够在这段时间内观看视频being. 但是当他们离开 PlayerVC 时，FavoritesVC 中的 collection 视图应该更新并且不再显示 Video .

当我删除一个 Video object 我使用 Realm 的 delete 方法。

这是我的代码，用于保存 Video objects:

的列表

/// Model class that manages the ordering of `Video` objects.
final class FavoriteList: Object {
    // MARK: - Properties

    /// `objectId` is set to a static value so that only
    /// one `FavoriteList` object could be saved into Realm.
    dynamic var objectId = 0

    let videos = List<Video>()

    // MARK: - Realm Meta Information

    override class func primaryKey() -> String? {
        return "objectId"
    }
}

这是我的 Video class 有一个 isFavorite 属性:

final class Video: Object {
    // MARK: - Properties

    dynamic var title = ""
    dynamic var descriptionText = ""
    dynamic var date = ""
    dynamic var videoId = ""
    dynamic var category = ""
    dynamic var duration = 0
    dynamic var fullURL = ""
    dynamic var creatorSite = ""
    dynamic var creatorName = ""
    dynamic var creatorURL = ""

    // MARK: FileManager Properties (Files are stored on disk for `Video` object).

    /*
        These are file names (e.g., myFile.mp4, myFile.jpg)
    */
    dynamic var previewLocalFileName: String?
    dynamic var stitchedImageLocalFileName: String?
    dynamic var placeholderLocalFileName: String?

    /*
        These are partial paths (e.g., bundleID/Feed/myFile.mp4,     bundleID/Favorites/myFile.mp4)
        They are used to build the full path/URL at runtime.
    */
    dynamic var previewLocalFilePath: String?
    dynamic var stitchedImageLocalFilePath: String?
    dynamic var placeholderLocalFilePath: String?

    // Other code...
}

这是我在 collection 视图中显示 Video object 的代码（注意：我使用 RealmCollectionChange 来更新 collection 视图用于删除和插入单元格）：

/// This view controller has a `collectioView` to show the favorites.
class FavoriteCollectionViewController: UIViewController {
    // MARK: Properties

    let favoriteList: FavoriteList = {
        let realm = try! Realm()
        return realm.objects(FavoriteList.self).first!
    }()

    // Realm notification token to update collection view.
    var notificationToken: NotificationToken?

    // MARK: Collection View

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return favoriteList.videos.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FavoritesCollectionViewCell.reuseIdentifier, for: indexPath) as! FavoritesCollectionViewCell
        cell.video = favoriteList.videos[indexPath.item]

        return cell
    }

    // I pass this lst forward to the PlayerVC
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        if let playerVC = self.storyboard?.instantiateViewController(withIdentifier: "PlayerViewController") as? PlayerViewController {
            // I pass the videos here.
            playerVC.videos = favoriteList.videos
            self.parent?.present(playerVC, animated: true, completion: nil)
        }
    }

    // MARK: Realm Notifications


    func updateUI(with changes: RealmCollectionChange<List<Video>>) {
        // This is code to update the collection view.
    }
}

最后，这是允许用户在所有 Video object 之间播放和循环的代码：

/// This view controller uses `AVFoundation` to play the videos from `FavoriteCollectionViewController`.
class PlayerViewControllerr: UIViewController {

    /// This `videos` is passed from `FavoriteCollectionViewController`
    var videos = List<Video>()

    // HELP: The app crashes here if I unfavorite a `Video`.
    @IBAction func didToggleStarButton(_ sender: UIButton) {
        let realm = try! Realm()
        try! realm.write {
            let videoToDelete = videos[currentIndexInVideosList] /// Get the video that is currently playing
            realm.delete(videoToDelete)
        }
    }
}

最终我希望不喜欢的Videoobject从Realm中完全删除。只是不确定 how/when 在这种情况下是否应该这样做。

有什么想法吗？

更新 1

解决这个问题的一个方法是：

制作 Video 副本的非托管副本，并使用该副本为视图控制器的 UI 供电。

我认为这可能有效的方式是：

PlayerVC 将收到两个 List，一个保存在 Realm 中的原始副本和一个 List 的副本，用于为 UI 供电。让我们调用列表 favoriteList 和 copyList.
所以在 didToggleStarButton 里面我们会做这样的事情：

代码：

/// This view controller uses `AVFoundation` to play the videos from `FavoriteCollectionViewController`.
class PlayerViewControllerr: UIViewController {

    /// A button to allow the user to favorite and unfavorite a `Video`
    @IBOutlet weak var starButton: UIButton!

    /// This is passed from `FavoriteCollectionViewController`
    var favoriteList: FavoriteList!

    /// A copy of the `FavoriteList` videos to power the UI.
    var copiedList: List<Video>!

    var currentIndexOfVideoInCopiedList: Int!

    override func viewDidLoad() {
        super viewDidLoad()

        // Make a copy of the favoriteList to power the UI.
        var copiedVideos = [Video]()

        for video in favoriteList.videos {
            let unmanagedVideo = Video(value: video)
            copiedVideos.append(unmanagedVideo)
        }

        self.copiedList.append(copiedVideos)
    }

    // HELP: The app crashes here if I unfavorite a `Video`.
    @IBAction func didToggleStarButton(_ sender: UIButton) {
        // Do the unfavoriting and favoriting here.


        // An example of unfavoriting:
        let realm = try! Realm()
        try! realm.write {
            let videoToDeleteFromFavoriteList = favoriteList.videos[currentIndexOfVideoInCopiedList] /// Get the video that is currently playing
            realm.delete(videoToDeleteFromOriginalList)
        }

        // Update star button to a new image depending on if the `Video` is favorited or not.
        starButton.isSelected = //... update based on if the `Video` in the `FavoriteList` or not.
    }
}

有什么想法吗？

Answer 1

这是解决方法。检查它是否有效。

 class PlayerViewControllerr: UIViewController {

          var arrayForIndex = [Int]()
          var videos = List<Video>()


          @IBAction func didToggleStarButton(_ sender: UIButton) {
               self.arrayForIndex.append(currentIndexInVideosList)     
           }

         @overide func viewWillDisappear(_ animated : Bool){
              super.viewWillDisappear(animated)
              for i in arrayForIndex{
                 let realm = try! Realm()
        try! realm.write {
            let videoToDelete = videos[i] /// Get the video that is currently playing
            realm.delete(videoToDelete)
        }
       }
        }

Answer 2

由于多种体系结构原因，这绝对是棘手的。

你是对的，你可以简单地从 FavoriteList.videos 中删除 object 然后在要关闭时从 Realm 中正确删除它控制器，但你是对的，如果用户点击主页按钮，或者应用程序在此之前崩溃，你最终会得到一个无头视频 object。你需要能够确保你可以跟踪它。

您可以考虑几件事。

在 Video class 中添加一个 isDeleted 属性。当用户取消收藏视频时，从 FavoriteList.videos 中删除 Video object，将属性设置为 true，但将其保留在 Realm 中。稍后（当应用程序退出或视图控制器被关闭时），您可以对所有 objects 进行一般查询，其中 isDeleted 是 true 然后删除它们（这解决了无头问题）。
由于您的体系结构需要一个依赖于模型的视图控制器，该模型可以从其下删除，具体取决于您从中使用了多少信息 Video object，它可能更安全制作 Video 副本的非托管副本，并使用该副本为视图控制器的 UI 供电。您可以通过 let unmanagedVideo = Video(value: video).

领域 - 删除后无法使用 object

Realm - Can't use object after having been deleted

objective-c

realm

ios

swift

realm-list

更新 1