Send and Receive MIDI with Swift and CoreMIDI

Question

I'm not very familiar with Swift/Objective-C or the Cocoa environment and I've been having a lot of trouble figuring out how to send or listen for data from a USB device with CoreMIDI. I'm trying to send the message (144, 36, 5) to my MIDI controller (an Ableton Push) which I have accomplished before using the Bitwig Studio Scripting API. I haven't been able to find much on this other than Apple's docs and they haven't been particularly helpful for me. So far I've figured out how to get a list of devices and check out their names, but beyond that I'm stuck.

What I've written so far trying to send MIDI:

var pushDevice = MIDIGetDevice(2)

var secondEntity = MIDIDeviceGetEntity(pushDevice, 1)

var pushDestination = MIDIEntityGetDestination(secondEntity, 0)

var midiPort = MIDIPortRef()

let myData : [Byte] = [ Byte(144), Byte(36), Byte(5) ]
var packet = UnsafeMutablePointer<MIDIPacket>.alloc(1)
var pkList = UnsafeMutablePointer<MIDIPacketList>.alloc(1)
packet = MIDIPacketListInit(pkList)
packet = MIDIPacketListAdd(pkList, 1024, packet, 0, 3, myData)

MIDISend(midiPort, pushDestination, pkList)

I feel like a bit of a goof for not being able to figure this out, I imagine it has to be a simple solution that I'm just not able to figure out for some reason. I don't think I'm properly constructing the MIDIPacketList or the MIDIPort, and I have no idea how to go about creating a callback and listening for MIDI messages.

Answer 1

I figured out how to send MIDI data by grabbing the device via it's unique ID. I'm not sure how memory management works in Swift, so keep that in mind. I will check back in later if I figure out how to properly create a callback and listen for MIDI input.

import Foundation
import CoreMIDI

var midiClient = MIDIClientRef()
var result = MIDIClientCreate("Foo Client", nil, nil, &midiClient)


var outputPort = MIDIPortRef()
result = MIDIOutputPortCreate(midiClient, "Output", &outputPort);

var endPoint = MIDIObjectRef()
var foundObj = MIDIObjectType()
result = MIDIObjectFindByUniqueID(UNIQUE_ID, &endPoint, &foundObj)

var pkt = UnsafeMutablePointer<MIDIPacket>.alloc(1)
var pktList = UnsafeMutablePointer<MIDIPacketList>.alloc(1)
let midiData : [Byte] = [Byte(144), Byte(36), Byte(5)]
pkt = MIDIPacketListInit(pktList)
pkt = MIDIPacketListAdd(pktList, 1024, pkt, 0, 3, midiData)

MIDISend(outputPort, endPoint, pktList)