Linker error: symbol(s) not found

Hello everyone,

I'm building my first Cocoa app (well, other than my "hello world"). I'm running into a strange problem when I try to build. The linker gives me the following error when I try to init a custom class (called 'RailsApp'):

Undefined symbols:
".objc class_nameRailsApp", referenced from:
literal-pointer@ _OBJC@__clsrefs@RailsApp in MainController.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

Now, there is an import statement in the header file to the 'RailsApp' header file. I've tried moving this around, etc to no avail. I really don't know what else I should do.

If anyone can help a beginner it'd be greatly appreciated!

Ernest