--- C++ to Objective-C callbacks. ---

---------
Requires:

For c++03 version:
- Boost.Preprocessor

For c++11 version:
- Nothing other than variadic templates

----------------
Compatible with:

- Boost.Function
- Boost.Signals
- Probably others :-)

---------------
Usage examples:

// in obj-c (ViewController for example):
// ...
- (void) emptyCallback 
{
	NSLog(@"In empty callback");
}

- (void) update:(float)delta
{ 
	// ... update something
}

- (int) mainWithArgc:(int)argc andArgv:(char**)argv
{
	// ... do something
	// and return a value
	return 0;
}

- (void) signalCallback
{
	// same as emptyCallback
}

boost::function<void()> cb1 = objc_callback<void()>(@selector(emptyCallback), self);
boost::function<void(float)> cb2 = objc_callback<void(float)>(@selector(update:), self);
boost::function<int(int, char**)> cb3 = objc_callback<int(int, char**)>(@selector(mainWithArgc:andArgv:), self);

// alternative (portable syntax):
boost::function1<void, float> cb2 = objc_callback_1<void, float>(@selector(update:), self);

// Boost.Signals example:
boost::signal<void()> sig;
sig.connect( objc_callback<void()>(@selector(signalCallback), self) );

// C++11 example:
auto cb = objc_callback<void(float)>(@selector(update:), self);

// somewhere else in c++-lands (your cross-platform c++ core application for example):
int main_app::run(int argc, char** argv)
{
	// ... somewhere later
	// ...

	// just invoke the callback
	cb1();

	// update 
	float delta = now() - last_update;
	cb2(delta);

	// run main (just example)
	int ret = cb3(argc, argv);

	// signal
	sig();
}