我的应用程序中有一个视频播放器。收藏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选定的视频。此外，您可以在这个新视图控制器中循环浏览集合视图中的所有视频，因为整个列表都已传递。
问题是：当用户在 中时PlayerVC，他们可以取消收藏Video. 如果他们这样做，我会Video从 Realm 中删除该对象。但是，这会导致：
Terminating app due to uncaught exception 'RLMException', reason: 'Object has been deleted or invalidated.'
基本上，如果用户正在观看视频PlayerVC并且他不喜欢视频，我希望他们暂时仍然能够观看视频。但是当他们离开时应该更新PlayerVC集合视图。FavoritesVCVideo
当我删除一个Video对象时，我使用 Realm 的delete方法。
这是我保存Video对象列表的代码：
/// 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类，它有一个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Video在集合视图中显示对象的代码（注意：我RealmCollectionChange用来更新集合视图以删除和插入单元格）：
/// 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对象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，我希望将不喜欢的Video对象从 Realm 中完全删除。只是不确定在这种情况下如何/何时执行此操作。
有什么想法吗？
更新 1
解决此问题的一种方法是：
- 制作副本的非托管副本
Video，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：
将
PlayerVC收到两个，一个保存在 Realm 中的原始文件和一个用于驱动 UIList的副本。List让我们称列表favoriteList和copyList.所以在里面
didToggleStarButton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？