Piano app in Swift

Question

I'm making my first app in Swift: a Piano app. I'd like to get your feedback especially about how I can make codes shorter. I maybe have to use arrays and loops and something, and searched by myself but couldn't get it.

view controller.swift

import UIKit
import AVFoundation

class ViewController: UIViewController {

var pianoSoundC3 = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("C3", ofType: "mp3")!)
var audioPlayerC3 = AVAudioPlayer()

var pianoSoundCS = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("C#", ofType: "mp3")!)
var audioPlayerCS = AVAudioPlayer()

var pianoSoundD = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("D", ofType: "mp3")!)
var audioPlayerD = AVAudioPlayer()

var pianoSoundDS = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("D#", ofType: "mp3")!)
var audioPlayerDS = AVAudioPlayer()

var pianoSoundE = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("E", ofType: "mp3")!)
var audioPlayerE = AVAudioPlayer()

var pianoSoundF = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("F", ofType: "mp3")!)
var audioPlayerF = AVAudioPlayer()

var pianoSoundFS = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("F#", ofType: "mp3")!)
var audioPlayerFS = AVAudioPlayer()

var pianoSoundG = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("G", ofType: "mp3")!)
var audioPlayerG = AVAudioPlayer()

var pianoSoundGS = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("G#", ofType: "mp3")!)
var audioPlayerGS = AVAudioPlayer()

var pianoSoundA = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("A", ofType: "mp3")!)
var audioPlayerA = AVAudioPlayer()

var pianoSoundAS = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("A#", ofType: "mp3")!)
var audioPlayerAS = AVAudioPlayer()

var pianoSoundB = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("B", ofType: "mp3")!)
var audioPlayerB = AVAudioPlayer()

var pianoSoundC4 = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("C4", ofType: "mp3")!)
var audioPlayerC4 = AVAudioPlayer()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    audioPlayerC3 = AVAudioPlayer(contentsOfURL: pianoSoundC3, error: nil)
    audioPlayerC3.prepareToPlay()

    audioPlayerCS = AVAudioPlayer(contentsOfURL: pianoSoundCS, error: nil)
    audioPlayerCS.prepareToPlay()

    audioPlayerD = AVAudioPlayer(contentsOfURL: pianoSoundD, error: nil)
    audioPlayerD.prepareToPlay()

    audioPlayerDS = AVAudioPlayer(contentsOfURL: pianoSoundDS, error: nil)
    audioPlayerDS.prepareToPlay()

    audioPlayerE = AVAudioPlayer(contentsOfURL: pianoSoundE, error: nil)
    audioPlayerE.prepareToPlay()

    audioPlayerF = AVAudioPlayer(contentsOfURL: pianoSoundF, error: nil)
    audioPlayerF.prepareToPlay()

    audioPlayerFS = AVAudioPlayer(contentsOfURL: pianoSoundFS, error: nil)
    audioPlayerFS.prepareToPlay()

    audioPlayerG = AVAudioPlayer(contentsOfURL: pianoSoundG, error: nil)
    audioPlayerG.prepareToPlay()

    audioPlayerGS = AVAudioPlayer(contentsOfURL: pianoSoundGS, error: nil)
    audioPlayerGS.prepareToPlay()

    audioPlayerA = AVAudioPlayer(contentsOfURL: pianoSoundA, error: nil)
    audioPlayerA.prepareToPlay()

    audioPlayerAS = AVAudioPlayer(contentsOfURL: pianoSoundAS, error: nil)
    audioPlayerAS.prepareToPlay()

    audioPlayerB = AVAudioPlayer(contentsOfURL: pianoSoundB, error: nil)
    audioPlayerB.prepareToPlay()

    audioPlayerC4 = AVAudioPlayer(contentsOfURL: pianoSoundC4, error: nil)
    audioPlayerC4.prepareToPlay()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

@IBAction func C3(sender: UIButton) {
    audioPlayerC3.currentTime = 0
    audioPlayerC3.play()
}

@IBAction func CS(sender: UIButton) {
    audioPlayerCS.currentTime = 0
    audioPlayerCS.play()
}

@IBAction func D(sender: UIButton) {
    audioPlayerD.currentTime = 0
    audioPlayerD.play()
}

@IBAction func DS(sender: UIButton) {
    audioPlayerDS.currentTime = 0
    audioPlayerDS.play()
}

@IBAction func E(sender: UIButton) {
    audioPlayerE.currentTime = 0
    audioPlayerE.play()
}

@IBAction func F(sender: UIButton) {
    audioPlayerF.currentTime = 0
    audioPlayerF.play()
}

@IBAction func FS(sender: UIButton) {
    audioPlayerFS.currentTime = 0
    audioPlayerFS.play()
}

@IBAction func G(sender: UIButton) {
    audioPlayerG.currentTime = 0
    audioPlayerG.play()
}

@IBAction func GS(sender: UIButton) {
    audioPlayerGS.currentTime = 0
    audioPlayerGS.play()
}

@IBAction func A(sender: UIButton) {
    audioPlayerA.currentTime = 0
    audioPlayerA.play()
}

@IBAction func AS(sender: UIButton) {
    audioPlayerAS.currentTime = 0
    audioPlayerAS.play()
}

@IBAction func B(sender: UIButton) {
    audioPlayerB.currentTime = 0
    audioPlayerB.play()
}

@IBAction func C4(sender: UIButton) {
    audioPlayerC4.currentTime = 0
    audioPlayerC4.play()
}

}

Answer 1

I think this should work. The key (pun intended) to making this work is to take advantage of the tag property of UIButton. In Interface Builder, set a different tag to each piano key. Start with 0 for "C3", 1 for "C#", up to 12 for "C4". Wire all of those keys to playKey.

import UIKit
import AVFoundation

class ViewController: UIViewController {

    let pianoKeys = ["C3", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B", "C4"]
    var audioPlayers:[AVAudioPlayer] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        for key in pianoKeys {
            let pianoSoundURL = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(key, ofType: "mp3")
            let audioPlayer = AVAudioPlayer(contentsOfURL: pianoSoundURL, error: nil)
            audioPlayer.prepareToPlay()
            audioPlayers.append(audioPlayer)
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func playKey(sender: UIButton) {
        let keynum = sender.tag
        audioPlayers[keynum].currentTime = 0
        audioPlayers[keynum].play()
    }
}