AVAudioPlayer doesn't stop while playing - ios

Question

I'm working on developing an app that plays narration by playing sentence-by-sentence sound file one after another.
With below code, it played as expected. However, after adding "Stop" button to stop what's playing, I found that "Stop" button didn't stop the sound.
I tested the "Stop" button before pressing "Play" button, which worked no problem (message was printed). However, after pressing "Play" and while NarrationPlayer is playing, "Stop" button didn't work (no message was printed).
Any idea what's wrong?
import UIKit
import AVFoundation
class ViewController: UIViewController,AVAudioPlayerDelegate {
var NarrationPlayer:AVAudioPlayer = AVAudioPlayer()
var soundlist: [String] = []
var counter = 0
}
func playSound(_ soundfile: String) {
let NarPath = Bundle.main.path(forResource: soundfile, ofType:"mp3")!
let NarUrl = URL(fileURLWithPath: NarPath)
do {
NarrationPlayer = try AVAudioPlayer(contentsOf: NarUrl)
NarrationPlayer.delegate = self
} catch{
print(error)
}
NarrationPlayer.play()
}
#IBAction func play(_ sender: Any) {
soundlist.append("a")
soundlist.append("b")
soundlist.append("c")
playSound("first")
while counter < soundlist.count{
if NarrationPlayer.isPlaying == true{
}
else{
playSound(soundlist[counter])
counter += 1
}
}
}
#IBAction func StopPlay(_ sender: Any) {
print("stop button worked")
}

Answer 1

The problem you're running into is that this line here:
while counter < soundlist.count{
is hogging the main thread, keeping any click on your "Stop Playing" button from actually firing.
You've set a delegate method though, and one of the very handy things you can do here is increment your counter and play your next sound file each time a sound file finishes up.
Something like this:
func playSound(_ soundfile: String) {
let NarPath = Bundle.main.path(forResource: soundfile, ofType:"mp3")!
let NarUrl = URL(fileURLWithPath: NarPath)
do {
NarrationPlayer = try AVAudioPlayer(contentsOf: NarUrl)
NarrationPlayer.delegate = self
} catch{
print(error)
}
NarrationPlayer.play()
}
func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool)
{
playSound(self.soundlist[counter])
counter += 1
}
#IBAction func play(_ sender: Any) {
playSound("first")
soundlist.append("a")
soundlist.append("b")
soundlist.append("c")
}
One last piece of advice:
Change the name NarrationPlayer to narrationPlayer. Variables in Swift, like in Objective-C, should start with lowercase (also known as lowerCamelCase).