title: Expression resolves to an unused function
body: <p>First of all let me say that I am very new to programming. What I'm trying to do is add a button that when pressed plays music, and when pressed again the music stops. Ideally when the button is pressed for a third time the music will have reset. Whilst trying to achieve this I'm getting the error message "Expression resolves to an unused function", as I am very new all the help I find online doesn't make any sense to me.</p>
  
  <pre><code>import UIKit
  import AVFoundation
  
  class ViewController: UIViewController {
      @IBOutlet weak var janitor: UIImageView!
      var pianoSound = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("C", ofType: "m4a")!)
      var audioPlayer = AVAudioPlayer()
  
      override func viewDidLoad() {
          super.viewDidLoad()
  
          audioPlayer = AVAudioPlayer(contentsOfURL: pianoSound, error: nil)
          audioPlayer.prepareToPlay()
      }
  
      override func didReceiveMemoryWarning() {
          super.didReceiveMemoryWarning()
      }
  
  
          @IBAction func PianoC(sender: AnyObject) {
  
          audioPlayer.play()
  
              if audioPlayer.playing { audioPlayer.stop} else {  audioPlayer.play}
  }
  }
  </code></pre>