No audio played

import UIKit
import AVFoundation

classViewController:UIViewController {

    varplayer —AVAudioPlayer?

    let sound_data = NSURL (fileURLWithPath: NSBundle.mainBundle().pathForResource("sample", ofType:"mp3")!)

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

        do{
            letplayer=try AVAudioPlayer(contentsOfURL:sound_data)
            player.play()
        }
        catchlet error as NSError {
            print(error)
        }

        player?prepareToPlay()

    }

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

    @ IBAction funcplay (sender: UIButton) {
        player?play()
    }

    @ IBAction func pause (sender: UIButton) {
        player?.pause()
    }

    @ IBAction func stop (sender: UIButton) {
        player?.stop()
        player?currentTime=0

    }
}