How to play NSData from Core Data in AVAudioPlayer - ios

Question

I save mp3 file into Core Data as NSData binary data. Then I load this file with help of NSFetchedResultsController. Then I wrote following code but I got the error. How can I fix it?
fatal error: unexpectedly found nil while unwrapping an Optional value
var audioPlayer = AVAudioPlayer()
func play() {
if musicData != nil {
audioPlayer = AVAudioPlayer(data: musicData, error: nil)
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)
AVAudioSession.sharedInstance().setActive(true, error: nil)
audioPlayer.prepareToPlay()
audioPlayer.play()
}
}
UPDATE
I checked it and I saw that AVAudioPlayer is nil but I init this player in beginning of this class.
Still I changed code but I get the same error
The second method
var av = AVAudioPlayer()
func play() {
let object = fetchedResultsController.fetchedObjects?.first as! Entity
let songData = object.mp3
var urlData: NSURL!
songData.writeToURL(urlData, atomically: true)
av = AVAudioPlayer(contentsOfURL: urlData, error: nil)
av.prepareToPlay()
av.play()
}

Answer 1

I added the file type hint and it works for me.
func playMusic() {
let url = NSBundle.mainBundle().URLForResource("Music", withExtension: "mp3")!
let data = NSData(contentsOfURL: url)!
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)
AVAudioSession.sharedInstance().setActive(true, error: nil)
audioPlayer = AVAudioPlayer(data: data, fileTypeHint: AVFileTypeMPEGLayer3, error: nil)
audioPlayer.prepareToPlay()
audioPlayer.play()
}

Answer 2

Had the same problem with playing mp3 file from Core Data. There is another solution, which don't require you to make resources, but only file manager . Works in Swift 5:
final class AudioPlayer: AVPlayer, ObservableObject {
private func changeSong(with newSong: Song) { // struct Song has function findInDatabase, which can return saved data from CoreData (or error)
// trying to find song in CoreData
newSong.findInDatabase() { (result: Result<SavedSong, CoreDataError>) in
switch result {
case .success(let savedSong):
// SavedSong struct has variable 'file' which is of type Data
guard let songFile = savedSong.file, !songFile.isEmpty else {
// your error handling
return
}
guard var localURL = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask).first else { return } // or error handling
localURL.appendPathComponent("song.mp3")
try! songFile.write(to: localURL) // saving song data in url
// now just playing from created URL
let nextPlayerItem = AVPlayerItem(url: localURL)
self.replaceCurrentItem(with: nextPlayerItem) // 'self' - is AVPlayer instance
self.play()
case .failure( _):
// error handling, for example try to play from URL
}
}
}
}