Question

Without going into specifics and breaking NDA…

If a developer preview of OSX shows me that a certain API is now part of the AppKit where I previously had to implement the API as a category of the class how do I arrange things so something built and linked against that future SDK will still run on on the current OS.

So in an abstract sense in the current SDK for Lion I have the method coolThing defined in a Category of the class NSFooBar so I can call

object.thing = fooBarInstance.coolThing

However the future SDK shows me that coolThing is now provided by the SDK and hence my category conflicts at build time.

Can I ensure that my Application still works on Lion (where the symbol will not be available) when Im linked against the future SDK without this sort of mess.

if(OSVersion == Lion) {
    return myImplementation;
}
else {
    return SDKNativeImplementaion;
}

Which I suppose I could hide away in the Category but it seems like a bit of mess.

Answer 1

That’s the reason you should prefix your category methods. So instead of coolThing, you could call it wb_coolThing or something like that. Your category method could check at runtime whether there is a coolThing method, call that if available or use your own implementation if not.