AVSpeechSynthesizer output as file?

As of now AVSpeechSynthesizer does not support this . There in no way get the audio file using AVSpeechSynthesizer . I tried this few weeks ago for one of my apps and found out that it is not possible , Also nothing has changed for AVSpeechSynthesizer in iOS 8.

I too thought of recording the sound as it is being played , but there are so many flaws with that approach like user might be using headphones, the system sound might be low or mute , it might catch other external sound, so its not advisable to go with that approach.

This is finally possible, in iOS 13 AVSpeechSynthesizer now has write(_:toBufferCallback:):

let synthesizer = AVSpeechSynthesizer()
let utterance = AVSpeechUtterance(string: "test 123")
utterance.voice = AVSpeechSynthesisVoice(language: "en")
var output: AVAudioFile?

synthesizer.write(utterance) { (buffer: AVAudioBuffer) in
   guard let pcmBuffer = buffer as? AVAudioPCMBuffer else {
      fatalError("unknown buffer type: \(buffer)")
   }
   if pcmBuffer.frameLength == 0 {
     // done
   } else {
     // append buffer to file
     if output == nil { 
       output = AVAudioFile(
         forWriting: URL(fileURLWithPath: "test.caf"), 
         settings: pcmBuffer.format.settings, 
         commonFormat: .pcmFormatInt16, 
         interleaved: false) 
     }
     output?.write(from: pcmBuffer)
   } 
}

You can use OSX to prepare AIFF files (or, maybe, some OSX-based service) via NSSpeechSynthesizer method startSpeakingString:toURL: