Retrieving the audio file from the document directory

Question

is it possible to retrieve the recorded audio file from the document directory? I have looked through the whole internet, but using AVAsset/WKAudioFileAsset does not seem to be the right path.

Is there just the way to convert the recorded audio file to NSData (binary format), send it to the server and then the server will convert the binary data back into the audio file?

I have found this here: https://iosdevcenters.blogspot.com/2016/04/save-and-get-image-from-document.html

(This example is about retrieving images and they have used UIImage) So, I am curious whether there is an equivalent way for retrieving an audio file? Is there a class for audio to save the file into that class just as UIImage for images?

I hope someone can help me out. Thank you very much.

My code looks as follows:

import WatchKit
import Foundation
import AVFoundation

class InterfaceController: WKInterfaceController, AVAudioRecorderDelegate{
    @IBOutlet weak var btn: WKInterfaceButton!
    var recordingSession : AVAudioSession!
    var audioRecorder : AVAudioRecorder!
    var settings = [String : Any]()

    override func awake(withContext context: Any?) {
        super.awake(withContext: context)
        recordingSession = AVAudioSession.sharedInstance()

        do{
            try recordingSession.setCategory(AVAudioSession.Category.playAndRecord)
            try recordingSession.setActive(true)
            recordingSession.requestRecordPermission(){[unowned self] allowed in
            DispatchQueue.main.async {
                if allowed{
                    print("Allow")
                } else{
                    print("Don't Allow")
                }
            }
        }
    }
        catch{
            print("failed to record!")
        }
        // Configure interface objects here.

   // Audio Settings

        settings = [
            AVFormatIDKey:Int(kAudioFormatLinearPCM),
            AVSampleRateKey:44100.0,
            AVNumberOfChannelsKey:1,
            AVLinearPCMBitDepthKey:8,
            AVLinearPCMIsFloatKey:false,
            AVLinearPCMIsBigEndianKey:false,
            AVEncoderAudioQualityKey:AVAudioQuality.max.rawValue

            ]

    }

    override func willActivate() {
        // This method is called when watch view controller is about to be visible to user
        super.willActivate()

        print("Test")
    }

    override func didDeactivate() {
        // This method is called when watch view controller is no longer visible
        super.didDeactivate()
    }


    func directoryURL() -> URL? {
        let fileManager = FileManager.default
        let urls = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
        let documentDirectory = urls[0] as URL
        let soundUrl = documentDirectory.appendingPathComponent("sound.wav")
  //      var soundUrlStr = soundUrl?.path
        //print(fileManager.fileExists(atPath: soundUrlStr))

        let filePath = (soundUrl).path
            print(filePath)

        print("URL")
        print(soundUrl)
        return soundUrl as URL?

    }



    func startRecording(){
        let audioSession = AVAudioSession.sharedInstance()

        do{
            audioRecorder = try AVAudioRecorder(url: self.directoryURL()! as URL,
            settings: settings)
            audioRecorder.delegate = self
            audioRecorder.prepareToRecord()
            audioRecorder.record(forDuration: 5.0)

        }
        catch {
            finishRecording(success: false)
        }

        do {
            try audioSession.setActive(true)
            audioRecorder.record()
        } catch {
        }
    }

    func finishRecording(success: Bool) {
        audioRecorder.stop()
        if success {
            print(success)
        } else {
            audioRecorder = nil
            print("Somthing Wrong.")
        }
    }


    @IBAction func recordAudio() {

        let path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
        let url = URL(fileURLWithPath: path)
        let pathPart = url.appendingPathComponent("sound.wav")
        let filePath = pathPart.path
        let fileManager = FileManager.default
        if fileManager.fileExists(atPath: filePath){
            print("File exists!")
            let audioAsset = WKAudioFileAsset(url:pathPart)
           // let playerItem  = WKAudioFilePlayerItem(asset:audioAsset)
            print("Audio File")
            print(audioAsset)
            print("WAV file")
            print(NSData(contentsOfFile: filePath) as Any)
        }else{
            print("File does not exist")
        }


        if audioRecorder == nil {
            print("Pressed")
            self.btn.setTitle("Stop")
            self.btn.setBackgroundColor(UIColor(red: 119.0/255.0, green: 119.0/255.0, blue: 119.0/255.0, alpha: 1.0))
            self.startRecording()


        } else {
            self.btn.setTitle("Record")
            print("Pressed2")
            self.btn.setBackgroundColor(UIColor(red: 221.0/255.0, green: 27.0/255.0, blue: 50.0/255.0, alpha: 1.0))
            self.finishRecording(success: true)

        }
    }

    func audioRecorderDidFinishRecording(_ recorder: AVAudioRecorder, successfully flag: Bool) {
        if !flag {
            finishRecording(success: false)
        }
    }

}