how do I set my Audio Session Default Behavior to Playback in swift?

My app has a "Click" sound functionality. I used the

import AVFoundation

then the following function to run the "Click" sound:

func playSound() {
    var soundPath = NSBundle.mainBundle().pathForResource("tick", ofType: "wav")
    var soundURL = NSURL.fileURLWithPath(soundPath!)
    self.audioPlayer = AVAudioPlayer(contentsOfURL: soundURL, error: nil)
    self.audioPlayer.play()
}

Now if the user is running a music player, my app causes the music player to stop. I read about the Audio Session Default Behavior in the documentation, but I don't know how to apply it.

Can you please help?

Thank you!