How to write HID function Handle_DeviceMatchingCallback in swift?

Question

I have a program on HID. But it is written in Objective-C. It is a project and my friends only know swift. So I thought of converting it to swift and I can't figure out how to write that function.

Obj-c Code:

 /* Creating The HID Manager */
 IOHIDManagerRef manager = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);
 /* Dictionary Matching - All the devices */
 IOHIDManagerSetDeviceMatching(manager,NULL);
 /* Connected and Disconnected Call Backs */
 IOHIDManagerRegisterDeviceMatchingCallback(manager,  &Handle_DeviceMatchingCallback , NULL);
 IOHIDManagerRegisterDeviceRemovalCallback(manager, &Handle_DeviceRemovalCallback,NULL);

And the call back functions are:

static void Handle_DeviceMatchingCallback(void *inContext,
                                          IOReturn inResult,
                                          void *inSender,
                                          IOHIDDeviceRef inIOHIDDeviceRef)
{
    printf("Connected\n");



}


static void Handle_DeviceRemovalCallback(void *inContext,
                                         IOReturn inResult,
                                         void *inSender,
                                         IOHIDDeviceRef inIOHIDDeviceRef)
{
    printf("Disconnected\n");
}

---

In swift,

I wrote Handle_DeviceMatchingCallback() as

func Handle_DeviceMatchingCallback(inContext: UnsafeMutableRawPointer!, inResult: IOReturn, inSender: UnsafeMutableRawPointer!, inIOHIDDeviceRef: IOHIDDevice)
{
    print("Connected")
}

But I can't pass the function to IOHIDManagerRegisterDeviceMatchingCallback() .

How to do that?

Answer 1

One way to handle your case is making the callbacks as closures:

let Handle_DeviceMatchingCallback: IOHIDDeviceCallback = {context, result, sender, device in
    print("Connected")
}
let Handle_DeviceRemovalCallback: IOHIDDeviceCallback = {context, result, sender, device in
    print("Disconnected")
}

---

Or else, you need to declare callback functions with exactly the same signature as defined in IOHIDDeviceCallback .

 typealias IOHIDDeviceCallback = (UnsafeMutableRawPointer?, IOReturn, UnsafeMutableRawPointer?, IOHIDDevice) -> Void 

(Taken from the Quick Help of Xcode.)

func Handle_DeviceMatchingCallback(_ context: UnsafeMutableRawPointer?, _ result: IOReturn, _ sender: UnsafeMutableRawPointer?, _ device: IOHIDDevice) {
    print("Connected")
}
func Handle_DeviceRemovalCallback(_ context: UnsafeMutableRawPointer?, _ result: IOReturn, _ sender: UnsafeMutableRawPointer?, _ device: IOHIDDevice) {
    print("Disconnected")
}