Swift MIDI Sampler setup

MIDISamplerSetup

class MIDISampler : NSObject {
    var engine:AVAudioEngine!
    var playerNode:AVAudioPlayerNode!
    var mixer:AVAudioMixerNode!
    var sampler:AVAudioUnitSampler!
    
    override init() {
        super.init()
        initAudioEngine()
    }
    
    func initAudioEngine () {
        engine = AVAudioEngine()
        playerNode = AVAudioPlayerNode()
        engine.attachNode(playerNode)
        mixer = engine.mainMixerNode
        engine.connect(playerNode, to: mixer, format: mixer.outputFormatForBus(0))
        
        // MIDI
        sampler = AVAudioUnitSampler()
        engine.attachNode(sampler)
        engine.connect(sampler, to: engine.outputNode, format: nil)