My Code

private let synthesizer = AVSpeechSynthesizer()

override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {

    self.contentHandler = contentHandler
    bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)

    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSession.Category.playback)

    let utterance = AVSpeechUtterance(string: "Hello Sim")
    utterance.voice = AVSpeechSynthesisVoice(language: "th_TH")
    utterance.rate = 1.0
    utterance.pitchMultiplier = 1.0
    utterance.volume = 1.0
    utterance.preUtteranceDelay = 0
    self.synthesizer.usesApplicationAudioSession = false
    self.synthesizer.speak(utterance)
    } catch {
    print(error.localizedDescription)
    }

    if let bestAttemptContent = self.bestAttemptContent {
        contentHandler(bestAttemptContent)
    }

}

Payload

{
    "aps":{
        "alert":{
            "title":"title"
            "subtitle":"subtitle"
            "body":"body"
        }
        "mutable-content":1
        "content-available":1
        "sound":"tester.caf"
    }
}

Info.plist UIBackgroundModes

• audio

• fetch

• processing

• remote-notification

This code can play in simulator but can’t play in real device !!

This code can play in simulator but can’t play in real device