Volume Changing using a slider in swift 2 - ios

Question

I have a UISlider added to my app and I am trying to figure out how to change the volume of the music playing. The music playing is being pulled from the iTunes Library using MPMusicPlayerController
Here is the viewDidLoad function with to show how I get the music from the iTunes Music library.
var musicPlayer = MPMusicPlayerController()
override func viewDidLoad() {
super.viewDidLoad()
musicPlayer = MPMusicPlayerController.systemMusicPlayer()
//Changing the Play/Pause Button
if musicPlayer.playbackState == MPMusicPlaybackState.Playing {
playPauseButton.setImage(UIImage(named: "Pause"), forState: UIControlState.Normal)
//Artwork
let currentItem: MPMediaItem = musicPlayer.nowPlayingItem!
let artwork: MPMediaItemArtwork = currentItem.valueForProperty(MPMediaItemPropertyArtwork) as! MPMediaItemArtwork
let artworkImage = artwork.imageWithSize(CGSize(width: self.view.frame.width, height: 372.0))
musicPlayerArtwork.image = artworkImage
musicBottomBackground.image = artworkImage
//Titel
let titleString: String = currentItem.valueForProperty(MPMediaItemPropertyTitle) as! String
songTitle.text = titleString as String
//Artist & Album
let artistString: String = currentItem.valueForProperty(MPMediaItemPropertyArtist) as! String
let albumString: String = currentItem.valueForProperty(MPMediaItemPropertyAlbumTitle) as! String
albumAndArtistTitle.text = "\(artistString) - \(albumString)"
} else {
playPauseButton.setImage(UIImage(named: "Play"), forState: UIControlState.Normal)
}
}
// I have IBAction functions linked to controlling the playbackk and pause functions that look like this one to play the music
func startPlayMusic() {
if self.musicPlayer.playbackState == MPMusicPlaybackState.Paused {
self.musicPlayer.play()
}
}
I have the slider hooked up with an IBAction and IBOutlet and have the following function to attempt adjusting the volume it:
var audioPlayer = AVAudioPlayer()
#IBAction func volumeSliderChanging(sender: UISlider) {
audioPlayer.volume = sender.value
}
Each time I try running this and moving the slider I get the following error
Any ideas what I could be doing wrong?

Answer 1

Your audioPlayer was not properly initiated. You should not call AVAudioPlayer(). Refer to the documentation for list of initializers that you should use. Here's an example:
let url = NSBundle.mainBundle().URLForResource("mySong", withExtension: "mp3")!
self.audioPlayer = try! AVAudioPlayer(contentsOfURL: url)