Use of extern in Objective C

Question

How good is it to use extern in Objective C? It does make coding for some parts easy.. but doesn\'t it spoil the object orientation?

Answer 1

There are some use cases for the extern keyword in Objective-C.
Aaron Hillegass suggests to create global notification names extern. e.g.:

extern NSString* const XYYourNotification;

You then define the actual NSString* in your implementation