How to share c# source between Unity projects?

Question

We have two projects underway and want to share some classes between them. The shared source must be in a single location so when a programmer on Project1 updates the code those changes are immediately seen in Project2.

The important part is that we do not want to maintain multiple copies of the same code. i think we would agree that its simply bad practise to do so.

The only option appears to be putting the code in a class library and load it as a plugin into each project. But I don't believe this works when referencing Unity types like GameObject or transform.

In C/C++ land we could put the source in a directory and include it into any solution we wanted - doesn't seem to be so easy in Unity-land. Is their a better way to share code between unity projects?

EDIT: All projects, including the shared code, are already under source control. This is not a Source Control question, its a framework issue. (And obviously I need to write better questions!)

Lets say the directory structure looks like this...

C:\ Project1\ Assets\ CodeForProject1\ StandardAssets\ Library\

C:\ Project2\ Assets\ CodeForProject2\ Resources\ Library\

D:\ UsefulCode\ PlayerClass\ WeaponsClass\ DataAccessClass\

Can Unity reference code from other projects? Can Unity reference code outside of its own Assets folder? If so, how?

Answer 1

I understand exactly what you're facing, we faced the same problem here some time ago.

The idea of our shared code is to be sort of a middleware, so it is natural that it will evolve through. Our solution was to create a git module for the shared code. I know you said that it's not a source control question, but at least here in my company, create a dll was not a good solution since we are changing the shared code constantly (we tried soft-links too, but it was very painful to maintain in all machines).

Here we created two projects: one for the middleware and another just for the tests. The last one have only the gitmodule to the middleware and a bunch of unit tests. We did it to ensure that there is no dependency to other projects. Both are in the source control. So when someone wants to implement a new feature inside the middleware, he/she make it inside the tests project, and when it's done commits to both projects.

Oh! And you can make a dll with Unity types and use them normally.