Multiple Module.PROJECTNAME.cpp files

Recently we went over what I assume is the limit a cpp source file can contain inside of it in our module files (generated by UBT) and its started splitting our code up into multiple.

Module.PROJECTNAME.1_of_3.cpp
Module.PROJECTNAME.2_of_3.cpp
Module.PROJECTNAME.3_of_3.cpp

Up until that point everything worked fine but once our code was split we started getting some undefined classes which was fixed by adding the appropriate includes to the appropriate headers from our game but most recently we’re experiencing unresolved externals. Looking at where this error is occurring we can see that the one class is in 1 of 3 and the class trying to reference that class is being compiled in 2 of 3.

What do we do to fix this?

Turns out our issue was caused by the body of some template functions having their definitions in the source file and not the header file. When we moved them our unresolved externals went away.