I have 2 functions. The first function can not be expose to objective c as it is a observer of core midi. The second function is visible to objective c so that I can pass data back to React Native.

To pass data between the 2 functions should I be using a struct or global variable.
I need the packet and source from function 1 passed to function 2. when adding @objc to the receive function I get error: Method cannot be marked @objc because the type of the parameter 2 cannot be represented in Objective-C

I figure to just save the data to global variable which works however not sure if I should use global variable or struct or is the whole things being constructed wrong

  func receive(_ packet: MIDIPacket, from source: MIDISource) {
      switch packet.message {
      case .noteOn, .noteOff, .controlChange, .pitchBendChange, .programChange:
        sendToReactNative()
      default:
          break
      }
  }
  
  @objc
  func sendToReactNative(){
    var data = ""
    sendEvent(withName: "onMidi", body: [data])
  }