Bluetooth headphones (Airpods) and AVAudioSession overriding

Question

I want to be able to use Airpods in my app, and I have some solution that works (almost).

func playSound(soundSpeech: String) {

    let audioSession = AVAudioSession.sharedInstance()        
    selectDevice(audioSession: audioSession)
    ...
}


func selectDevice(audioSession: AVAudioSession) {

    print("select device")

    var headphonesExist = false
    var bluetoothExist = false
    var speakerExist = false

    let currentRoute = AVAudioSession.sharedInstance().currentRoute

    for output in audioSession.currentRoute.outputs {
        print(output)

        if output.portType == AVAudioSessionPortHeadphones || output.portType == AVAudioSessionPortHeadsetMic {
            headphonesExist = true
        }

        if output.portType == AVAudioSessionPortBluetoothA2DP || output.portType == AVAudioSessionPortBluetoothHFP {
            bluetoothExist = true
            print("bluetooth is enabled")
        }

        if output.portType == AVAudioSessionPortBuiltInSpeaker {
            speakerExist = true
        }
    }

    print("headphones: \(headphonesExist) bluetooth: \(bluetoothExist) speakerExist: \(speakerExist)")

    if bluetoothExist == true {
        do { try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, with: AVAudioSessionCategoryOptions.allowBluetoothA2DP) } catch {
            print("error with audiosession: bluetooth")
        }
    } else {
        do { try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, with: AVAudioSessionCategoryOptions.defaultToSpeaker) } catch {
            print("error with audiosession: default speaker")
        }
    }
}

The problem is it does work only if (or after) I switch to other app with sound (i.e. YouTube app) and back. After that it works like a charm, but I believe it should work from the start.