Changing the volume of an SCNAudioPlayer in real time - Swift

I know a similar question was asked here...(https://forums.developer.apple.com/thread/27681)...but it doesnt give an example of how to do it which is what I am after as I can't work it out from the information provided.

I am trying to work out how I can change the volume of an

SCNAudioPlayer

in real time.

Currently, I have an

SCNAudioSource

connected to an

SCNAudioPlayer

. This audio player is then assigned to a

SCNNode

so that my sound makes use of SceneKits spatial audio processing.

As it stands, I am able to change the volume of each

SCNNode

using

SCNAudioSource.volume

triggered by the boolean variable

vol

. An extract of my code for this is shown below:

(audioSource, audioCount) = soundFileSelect(audioFileIndex: 0) 
audioSource?.isPositional = true 
if vol { 
audioSource?.volume = 1.0 
} 
else { 
audioSource?.volume = 0.0 
} 
let audioPlayer = SCNAudioPlayer(source: audioSource!) 
geometryNode.addAudioPlayer(audioPlayer) 
let play = SCNAction.playAudio(audioSource!, waitForCompletion: true) 
let loopPlay = SCNAction.repeatForever(play) 
geometryNode.runAction(loopPlay)

However, this only changes the default volume setting of the audio source, and so only happens when the node is spawned. I am trying to change the volume of it in real time, after a button press.

I feel I am missing something very simple, and have trolled the internet for documentation and examples but am really struggling. From Apple's API documentation I am fairly certain it can be done. As far as I can tell you have to use the

audioNode

property associated with the

SCNAudioPlayer

which forms part of the

AVAudioMixing

protocol. Using this

AVAudioMxing

volume property should be what I need!

However, for the life of me I can't work out how to implement this process in code within my current setup. I can access

mainMixer.volume

/

outputvolume

such as:

audioPlayer.audioNode?.engine?.mainMixerNode.outputVolume=0

but this doesn't seem to have any effect.

How do the AV and SCN components link together?

Any help or examples of how one goes about implementing this would be hugely appreciated!

Thanks in advanced.