Working with iPadOS 14 Beta 3.

import Foundation
import SwiftUI
import AVFoundation

class AudioHandler: NSObject, ObservableObject, AVAudioPlayerDelegate {

    @Published var isPlaying: Bool = false {
        willSet {
            if newValue == true {
                playAudio()
            }
        }
    }

    var myAudioPlayer = AVAudioPlayer()
    var fileName = ""

    override init() {
        super.init()
        myAudioPlayer.delegate = self
    }

    func playAudio() {
        let path = Bundle.main.path(forResource: fileName, ofType:nil)!
        let url = URL(fileURLWithPath: path)

        do {
            myAudioPlayer = try AVAudioPlayer(contentsOf: url)
            myAudioPlayer.play()
        } catch {
            // couldn't load file :(
        }
    }

    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {
        print("Did finish Playing")
        isPlaying = false
    }
}

Usage

if audioHandler.isPlaying == false {

                            Button(action: {
                                audioHandler.fileName = event.fileName
                                audioHandler.isPlaying.toggle()

                                print("Button Tapped")
                            }) {
                                Image(systemName: "play.circle")
                                    .font(.largeTitle)
                                    .foregroundColor(Color.white)
                            }
                        }

Click on the button, it plays the audio file. The audioPlayerDidFinishPlaying is never called. Tested on the device. I have a similar class for SpeechSythesis, and the (speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance)) works fine. Is something up with AVAudioPlayerDelegate, or am I doing something wrong?

Just in case you've not got this working yet, all you need to do is move the delegate assignment out of the initialiser until after myAudioPlayer is instantiated.

So :-

override init() {
        super.init()
        // not here: myAudioPlayer.delegate = self
    }

func playAudio() {
        let path = Bundle.main.path(forResource: fileName, ofType:nil)!
        let url = URL(fileURLWithPath: path)

        do {
            myAudioPlayer = try AVAudioPlayer(contentsOf: url)
            myAudioPlayer.delegate = self    // Add here (once myAudioPlayer is instantiated)
            myAudioPlayer.play()
        } catch {
            // couldn't load file :(
        }
    }

Apologies if there's a better way of assigning the delegate but this worked for me. G