C++ Static variable and unresolved externals error

Question

I was hoping I could get some clarification on static variables of a class.

For example: I have two different classes which perform completely different functions,

Answer 1

static variables inside a class must still be defined somewhere, just like methods:

Put this in main.cpp:

beta alpha::var;

Answer 2

Add this to main.cpp:

beta  alpha::var;

var in h-file is only type declaration. Variable should be created in some source file.