Counting Up and Down using Volume buttons on iOS (Swift) - ios

Question

Hi I creating an app for myself, where I want to count and display the # on the screen. I want to use the volume buttons to count up and down. I was able create a button on screen to count up and down but I want to use the physical buttons. I have listed what I have so far, but the volume buttons doesn't seem to work. I've replaced AVAudioSession with AVAudioPlayer hoping to control the volume with the slider. I get a error EXC_BAD_ACCESS (Code=1, Adress=0x48)
import UIKit
import AVFoundation
class ViewController: UIViewController {
var audioPlayer = AVAudioPlayer()
#IBOutlet weak var counter: UILabel!
#IBOutlet weak var tapCounterUp: UIButton!
#IBOutlet weak var tapCounterDown: UIButton!
#IBOutlet weak var tapReset: UIButton!
#IBOutlet weak var volumeController: UISlider!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
//Starts the count at 0
var count : Int = 0
//Adds +1 to Count
#IBAction func buttonUp(_ sender: Any) {
count += 1
counter.text = String(count)
}
//Subtracts -1 to Count
#IBAction func buttonDown(_ sender: Any) {
count -= 1
counter.text = String(count)
}
//Resets the Count to "0"
#IBAction func buttonReset(_ sender: Any) {
count = 0
counter.text = String(count)
}
//Volume Controller
#IBAction func volumeControl(_ sender: UISlider) {
let sliderValue = lroundf(sender.value)
counter.text = "\(sliderValue)"
/// **This is were the Error occurs.**
audioPlayer.volume = volumeController.value
}
// End of function, don't delete
}