Auto-detect USB Device Connect/Disconnect - macos

Question

I have a Cocoa app that needs to be notified whenever a device is connected or disconnected from a USB port. I can get the DeviceConnected callback to work, but the DeviceDisconnected function does not get called when disconnecting a USB device.
Below is my code:
+ (void)listenForUSBEvents
{
io_iterator_t portIterator = 0;
CFMutableDictionaryRef matchingDict = IOServiceMatching( kIOUSBDeviceClassName );
IONotificationPortRef notifyPort = IONotificationPortCreate( kIOMasterPortDefault );
CFRunLoopSourceRef runLoopSource = IONotificationPortGetRunLoopSource( notifyPort );
CFRunLoopRef runLoop = CFRunLoopGetCurrent();
CFRunLoopAddSource( runLoop, runLoopSource, kCFRunLoopDefaultMode);
CFRetain( matchingDict );
kern_return_t returnCode = IOServiceAddMatchingNotification( notifyPort, kIOMatchedNotification, matchingDict, DeviceConnected, NULL, &portIterator );
if ( returnCode == 0 )
{
DeviceConnected( nil, portIterator );
}
returnCode = IOServiceAddMatchingNotification( notifyPort, kIOMatchedNotification, matchingDict, DeviceDisconnected, NULL, &portIterator );
if ( returnCode == 0 )
{
DeviceDisconnected( nil, portIterator );
}
}
#end
void DeviceConnected( void *refCon, io_iterator_t iterator )
{
kern_return_t returnCode = KERN_FAILURE;
io_object_t usbDevice;
while ( ( usbDevice = IOIteratorNext( iterator ) ) )
{
io_name_t name;
returnCode = IORegistryEntryGetName( usbDevice, name );
if ( returnCode != KERN_SUCCESS )
{
return;
}
[[NSNotificationCenter defaultCenter] postNotificationName:deviceConnectedNotification object:nil userInfo:nil];
}
}
void DeviceDisconnected( void *refCon, io_iterator_t iterator )
{
[[NSNotificationCenter defaultCenter] postNotificationName:deviceDiconnectedNotification object:nil userInfo:nil];
}

Answer 1

I figured out what I was doing wrong.
First of all, IOServiceAddMatchingNotification for deviceDisconnected should look like this:
returnCode = IOServiceAddMatchingNotification( notifyPort, kIOTerminatedNotification, matchingDict, DeviceDisconnected, NULL, &portIterator );
Second, the DeviceDisconnected function should look like this:
void DeviceDisconnected( void *refCon, io_iterator_t iterator )
{
kern_return_t returnCode = KERN_FAILURE;
io_object_t usbDevice;
while ( ( usbDevice = ioIteratorNext( iterator ) ) )
{
returnCode = IOObjectRelease( usbDevice );
if ( returnCode != kIOReturnSuccess )
{
NSLog( #"Couldn't release raw device object: %08x.", returnCode );
}
}
[[NSNotificationCenter defaultCenter] postNotificationName:deviceDiconnectedNotification object:nil userInfo:nil];
}