How to modify Engine's output on iOS AudioKit - ios

Question

I want to choose different sound effects to listen to when playing music
this is my code:
class EffectConductor: ObservableObject, ProcessesPlayerInput {
var engine = AudioEngine()
var player = AudioPlayer()
// var dryWetMixer : DryWetMixer
var isPlaying = false
init(path:String) {
let mediaUrl = URL.init(fileURLWithPath: path)
let file = try! AVAudioFile(forReading: mediaUrl)
try! player.load(file: file, buffered: true)
engine.output = player
}
#Published var effectType: Int = 0 {
didSet {
var node : Node? = nil
switch effectType {
case 1:
node = AutoPanner(player)
case 2:
node = AutoWah(player)
case 3:
node = Compressor(player)
case 4:
node = DynamicRangeCompressor(player)
case 5:
node = Expander(player)
case 6:
node = Phaser(player)
case 7:
node = StringResonator(player)
default:
node = nil
}
if node==nil
{
print("effect nil")
engine.output = player
}else{
engine.output = DryWetMixer(player, node!)
}
}
}
}
when i call this code：
engine.start() player.start()
Can play music. but when i click a button and call this code:
effectType = 2(or ever value)
to change engine.output value
it's stop playing
i try this when i click a button
let progress = player.getCurrentTime()
if(isPlaying){
player.stop()
}
self.effectType = 3
if(isPlaying){
player.seek(time: progress)
player.play()
}
But there will be a pause in the playback process
how to solve this problem?
thanks everyone!