Undefined Symbols Error -- in Prog 11.1!

[Learner]

I have correctly completed the program 11.1 for adding a category to the Fraction class. However, when I used the terminal to run the program, I get this:

Undefined symbols:
  "_gCounter", referenced from:
      +[Fraction allocF] in ccdAhuuP.o
      +[Fraction allocF] in ccdAhuuP.o
      +[Fraction count] in ccdAhuuP.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

This allocF is from chapter 10.

I used the gcc compiler statement:

gcc -framework Foundation Fraction.m NewFraction.m -o Main

NewFraction.m is the name of the program with all the interface, implementation, and main.m code for prog 11.1

Not sure why it's giving me that error, especially since I haven't even called that particular method.

[Learner]

Problem solved.

I forgot to put the

Code: (Objective-C)

 static int gCounter;

at the top of the Fraction.m file.