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()
}
}

• Matt Gibson: It's worth nothing that if you can penetrate the documentation, Apple actually provides AUSampler, which can load a custom set of samples into a MIDI instrument. It's basically designed to do exactly what you're doing here, only it uses a preprepared bundle of samples, loads in one step, and then you can fire MIDI commands at it rather than working a whole bunch of AVAudioPlayers.

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()
 }
}

• Bick: It worked! now I come to understand Arrays, for in, and .tag property. Thank you very much!