Drum pad sample using AudioKit

ViewController

import UIKit

class ViewController: UIViewController {
    
    var buttons: [UIButton] = []
    var notes: [AKNote] = []
    let soundFiles: Array<String> = ["BassC1", "FluteC2", "glockA1", "musicboxC1", "newharpC1", "pianoguitarA2"]
    
    func prepareSounds() {
        for (index, soundFile) in enumerate(soundFiles) {
            var fileName = NSBundle.mainBundle().pathForResource(soundFile, ofType: "aif")
            var akSoundFile = AKSoundFile(filename: fileName)
            var instrument = AKInstrument()
            instrument.addFunctionTable(akSoundFile)
            var looper = AKMonoSoundFileLooper(soundFile: akSoundFile)
            looper.loopMode = AKSoundFileLooperMode.NoLoop
            instrument.connect(looper)
            var output = AKAudioOutput(audioSource: looper)
            instrument.connect(output)
            var note: AKNote = AKNote()
            note.instrument = instrument
            notes.append(note)
            AKOrchestra.addInstrument(instrument)
        }
        AKOrchestra.start()
    }
    
    func playSound(sender: UIButton!) {
        var tag: Int = sender.tag
        notes[tag].play()
    }
    
    func setupGUI() {
        var viewsDict = Dictionary <String, UIView>()
        var visualFormatVertical = "V:|-30"
        for var i = 0; i < 5; i++ {
            var button: UIButton = UIButton.buttonWithType(UIButtonType.System) as UIButton
            button.setTitle(String(i), forState: UIControlState.Normal)
            button.backgroundColor = UIColor.blackColor()
            button.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)
            button.setTranslatesAutoresizingMaskIntoConstraints(false)
            button.addTarget(self, action: "playSound:", forControlEvents: .TouchUpInside)
            button.tag = i
            view.addSubview(button)
            buttons.append(button)
            
            viewsDict["Button"+String(i)] = button
            view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(
                "H:|-[Button"+String(i)+"]-|", options: nil, metrics: nil, views: viewsDict))
            visualFormatVertical += "-[Button"+String(i)+"]-10"
        }
        visualFormatVertical += "-|"

        view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(visualFormatVertical, options: nil, metrics: nil, views: viewsDict))
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        prepareSounds()
        setupGUI()
    }

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

}