CODEWITHSUNDEEP
objective-cxcode
NimaM
NimaM

Reputation: 33

Converting from C to Objective-c

How should I write this code in objective-c:

kr = IOServiceAddMatchingNotification(gNotifyPort, 
       kIOFirstMatchNotification, matchingDict, RawDeviceAdded, NULL, &gRawAddedIter);

I tried this one:

kr = IOServiceAddMatchingNotification(gNotifyPort, kIOFirstMatchNotification,
 matchingDict, @selector(RawDeviceAdded), NULL, &gRawAddedIter);

and the function look like:

(void)RawDeviceAdded:(void *)refCon iterator:(io_iterator_t)iterator
{
  .....
}

I am not sure if its right.

Upvotes: 2

Views: 378

Answers (1)

trojanfoe
trojanfoe

Reputation: 122381

Short answer is: You can't do that directly.

This is because IOKit is a C-API so any callback functions it requires must be C, and not Objective-C.

That's not to say that you can't mix C and Objective-C, and use the C callback function to trampoline to your Objective-C method. It's simply a matter of getting the reference to the class to the C callback function; in this particular case that's using refCon.

SomeObjcClass.m:

// Objective-C method (note that refCon is not a parameter as that
// has no meaning in the Objective-C method)
-(void)RawDeviceAdded:(io_iterator_t)iterator
{
    // Do something
}

// C callback "trampoline" function
static void DeviceAdded(void *refCon, io_iterator_t iterator)
{
    SomeObjcClass *obj = (SomeObjcClass *)refCon;
    [obj RawDeviceAdded:iterator];
}

- (void)someMethod
{
    // Call C-API, using a C callback function as a trampoline
    kr = IOServiceAddMatchingNotification(gNotifyPort,
                                          kIOFirstMatchNotification,
                                          matchingDict,
                                          DeviceAdded,    // trampoline function
                                          self,           // refCon to trampoline
                                          &gAddedIter
                                          );        

}

Upvotes: 3

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