Second cached video being used for all cells? - ios

Question

I attempted the following caching mechanism to cache videos which are added in cells in my app:
import Foundation
public enum Result<T> {
case success(T)
case failure(NSError)
}
class CacheManager {
static let shared = CacheManager()
private let fileManager = FileManager.default
private lazy var mainDirectoryUrl: URL = {
let documentsUrl = self.fileManager.urls(for: .cachesDirectory, in: .userDomainMask).first!
return documentsUrl
}()
func getFileWith(stringUrl: String, completionHandler: #escaping (Result<URL>) -> Void ) {
let file = directoryFor(stringUrl: stringUrl)
//return file path if already exists in cache directory
guard !fileManager.fileExists(atPath: file.path) else {
completionHandler(Result.success(file))
return
}
DispatchQueue.global().async {
if let videoData = NSData(contentsOf: URL(string: stringUrl)!) {
videoData.write(to: file, atomically: true)
DispatchQueue.main.async {
completionHandler(Result.success(file))
}
} else {
DispatchQueue.main.async {
let error = NSError(domain: "SomeErrorDomain", code: -2001 /* some error code */, userInfo: ["description": "Can't download video"])
completionHandler(Result.failure(error))
}
}
}
}
private func directoryFor(stringUrl: String) -> URL {
let fileURL = URL(string: stringUrl)!.lastPathComponent
let file = self.mainDirectoryUrl.appendingPathComponent(fileURL)
return file
}
}
Used like this for each cell if at that index it is a video:
CacheManager.shared.getFileWith(stringUrl: videoURL) { result in
switch result {
case .success(let url):
let player = AVPlayer(url: url)
let playerLayer = AVPlayerLayer(player: player)
playerLayer.frame = CGRect(x: -8, y: 0, width: 138, height: 217)
cell.imageOrVideoView.layer.addSublayer(playerLayer)//seems to use the the first video for all videos...
cell.profImage.sd_setImage(with: URL(string: "\(self.postArray[indexPath.item].user.profileImageUrlString!)"), placeholderImage: UIImage(named: "media"))
break;
// do some magic with path to saved video
case .failure(let error):
print(error, " failure in the Cache of video")
break;
// handle errror
}
}
The problem with this is that now the second video URL is used as the video (which I don't play) for every single video cell.
Do I need to reload cache? This seems wrong...
I have found that this seems to be the problematic code:
//return file path if already exists in cache directory
guard !fileManager.fileExists(atPath: file.path) else {
completionHandler(Result.success(file))
return
}
When commenting out the guard each cell does get the correct video. The problem is that it does not cache it. How can I fix this?
Edit:
I found something weird which may be a symptom of the problem. if at the index path the cell should be a video, then I print video else it must be a image print image. When looking in the console however, I see that image gets printed 5 times and video gets printed 2, even though there are 11 cells in the collection view. Also I can confirm that regardless of which it is I print "in here" which gets printed 7 times. Again, this all when (when you scroll), there are 11 cells all of which should be different but of course all the video ones have the second videos first frame.

Answer 1

What happens is when the first cell is dequeued you get it with it's video layer added successfully then when you scroll this callback
CacheManager.shared.getFileWith(stringUrl: videoURL) { result in
is very slow so the previous cell content appears at that time making the fact that it's the second cell in all cells and that because of cell dequeuing
You have to clear the previous layers before the above line which is caused by
cell.imageOrVideoView.layer.addSublayer(playerLayer)
Edit: after the dequeue line do
cell.imageOrVideoView.layer.sublayers?.forEach {
if $0 is AVPlayerLayer {
$0.removeFromSuperlayer()
}
}

Answer 2

The problem seemed to be tied to using the cache manager for each cell. and the fact that I download a video for each cell. Instead used the thumbnail for each image which I then had to save.