如何下载并保存音频文件，然后在swift中播放？

import UIKit
import AVFoundation

class ViewController: UIViewController {
    var audioPlayer: AVAudioPlayer?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 下载并保存音频文件
        downloadAndSaveAudioFile()
        
        // 播放音频文件
        playAudio()
    }
    
    func downloadAndSaveAudioFile() {
        guard let audioURL = URL(string: "https://example.com/audio.mp3") else {
            return
        }
        
        let downloadTask = URLSession.shared.downloadTask(with: audioURL) { (location, response, error) in
            guard let location = location else {
                return
            }
            
            let documentsDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
            let destinationURL = documentsDirectoryURL.appendingPathComponent("audio.mp3")
            
            do {
                try FileManager.default.moveItem(at: location, to: destinationURL)
            } catch {
                print("Failed to save audio file: \(error)")
            }
        }
        
        downloadTask.resume()
    }
    
    func playAudio() {
        let documentsDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
        let audioURL = documentsDirectoryURL.appendingPathComponent("audio.mp3")
        
        do {
            audioPlayer = try AVAudioPlayer(contentsOf: audioURL)
            audioPlayer?.play()
        } catch {
            print("Failed to play audio: \(error)")
        }
    }
}