swift – 表达式解析为未使用的函数

首先让我说我对编程很新.我想要做的是添加一个按钮,当按下播放音乐时,再次按下音乐停止.理想情况下,第三次按下按钮时,音乐将重置.在尝试实现这一点时,我收到错误消息“表达式解析为未使用的功能”,因为我非常新的所有的帮助,我在网上找到没有任何意义.

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}
}
}

if audioPlayer.playing { audioPlayer.stop} else {  audioPlayer.play}

if audioPlayer.playing { 
    audioPlayer.stop()
} else {  
    audioPlayer.play()
}