“Undefined symbols” linker error with simple template class

Question

Been away from C++ for a few years and am getting a linker error from the following code:

Gene.h

#ifndef GENE_H_INCLUDED
#define GENE_H_INCLUDED

tem         


        

Answer 1

The template definition (the cpp file in your code) has to be included prior to instantiating a given template class, so you either have to include function definitions in the header, or #include the cpp file prior to using the class (or do explicit instantiations if you have a limited number of them).