AVAudioPlayer fade volume out

Question

I have an AVAudioPlayer playing some audio (duh!)

The audio is initiated when the user presses a button. When they release it I want the audio to fade out.

I

Answer 1

Swift 3

I like Ambroise Collon answer's , so i voted up but Swift is statically typed so the performSelector: methods are to fall by the wayside, maybe an alternative could be dispatch async (in this version I've added also the destination volume as parameter)

func dispatchDelay(delay:Double, closure:@escaping ()->()) {
    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delay, execute: closure)
}

extension AVAudioPlayer {
    func fadeOut(vol:Float) {
        if volume > vol {
            //print("vol is : \(vol) and volume is: \(volume)")
            dispatchDelay(delay: 0.1, closure: {
                [weak self] in
                guard let strongSelf = self else { return }
                strongSelf.volume -= 0.01
                strongSelf.fadeOut(vol: vol)
            })
        } else {
            volume = vol
        }
    }
    func fadeIn(vol:Float) {
        if volume < vol {
            dispatchDelay(delay: 0.1, closure: {
                [weak self] in
                guard let strongSelf = self else { return }
                strongSelf.volume += 0.01
                strongSelf.fadeIn(vol: vol)
            })
        } else {
            volume = vol
        }
    }
}