NSNumber constants in Obj-C

You can basically achieve close to what you want in three parts:

.h file:

extern NSNumber *MyFirstConstant;

.m file

NSNumber *MyFirstConstant;

AppDelegate.m

+(void)initialize
{
    MyFirstConstant = @5;
    ...
}

AppDelegate is guaranteed to run before any of your other code, and the initialize is the first method that would be called on AppDelegate, so you can essentially insure all your constants are setup for you before your app runs.