I needed to define this callback:
typedef void (*MIDIReadProc) ( const MIDIPacketList *pktlist, void *readProcRefCon, void *srcConnRefCon );
and I wanted to use Objective-C as least as possible.
This was my approach:
MIDIReadProcCallback.h
#import <Foundation/Foundation.h>
#import <AudioToolbox/AudioToolbox.h>
typedef void (^OnCallback)(const MIDIPacketList *packetList);
@interface MIDIReadProcCallback : NSObject
+ (void (*)(const MIDIPacketList *pktlist, void *readProcRefCon, void *srcConnRefCon))midiReadProc;
+ (void)setOnCallback:(OnCallback)onCallback;
@end
MIDIReadProcCallback.m
#import "MIDIReadProcCallback.h"
static OnCallback _onCallback = nil;
static void readProcCallback(const MIDIPacketList *pktlist, void *refCon, void *connRefCon) {
if (_onCallback) {
_onCallback(pktlist);
}
}
@implementation MIDIReadProcCallback
+ (void (*)(const MIDIPacketList *pktlist, void *readProcRefCon, void *srcConnRefCon))midiReadProc {
return readProcCallback;
}
+ (void)setOnCallback:(OnCallback)onCallback {
_onCallback = onCallback;
}
@end
Then you can register MIDIReadProcCallback.midiReadProc
as callback and set handler MIDIReadProcCallback.setOnCallback({ (packetList: MIDIPacketList) in ... })