[SOLVED] Safe to use matching CFBridging calls to transfer in and out of ARC for non CF types?

Safe to use matching CFBridging calls to transfer in and out of ARC for non CF types?

I'm writing a game using the Chipmunk physics engine, and I'd like to store a pointer to an Objective-C object in every body's userData field. I know I need to use a bridging cast to cast between id and void *, but I'm not sure the way I'm doing it is safe:

// When body is created
cpBody *body = cpBodyNew(...);
UserData *userData = [[UserData alloc] init];
cpBodySetUserData(body, CFBridgingRetain(body));

...

// When body is destroyed
UserData *userData = cpBodyGetUserData(body);
CFBridgingRelease(userData);
cpBodyFree(body);

This code seems to work, but I've also read that you're only supposed to use CFBridging*() on objects that can be toll-free bridged to Core Foundation types. Since UserData is derived from NSObject, and NSObject isn't on the list of toll-free bridged types, I seem to be breaking that rule.

Is my code okay because I eventually call CFBridgingRelease and don't try to pass the object to any other Core Foundation functions, or is there another way I should be going about transferring Objective-C objects in and out of C?

Solution

It's safe. NSObject is toll-free bridged to a generic CFTypeRef. Also, I'm assuming you aren't calling any other Core Foundation functions on the void*, so it hardly matters.