Duplicate Functionality Amongst Multiple Projects

Question

I'm currently working on two social networking sites that have a lot in common, yet are distinctively different. I find myself writing a lot of the same code for both (including UI), and was wondering if there is a best practice that will limit duplicating code.

One of the main problems is that these projects are very independent of eachother and will likely have more differences than similaries soon. Also, once the initial work is done, they might be handed off to other programmers, so having shared code libraries might end up being a big problem.

Any suggestions from people that might have had to deal with a similiar situation?

PS: I'm the only developer on both of these projects, and it looks like it's going to stay that way for a while.

Answer 1

Abstracting shared functionality back to a framework or library with defined interfaces and default implementations is a common way to handle this. For example, your plugin architecture, if you choose to support one, is probably something that could be shared among all of your projects. Most of the time the things you want to share are pretty basic functionality or relatively abstract functionality that can be easily customized. The former are easier to recognize and factor out to common libraries. The latter may sometimes be more work than simply re-implementing the code with minor changes (sharing patterns rather than code).

One thing you want to be careful of is to let the actual re-use drive the design of common libraries rather than coming up with a shared architecture in advance. It's very tempting to get caught up in framework design and abstracting it out for shared use. Unfortunately you often find that the shared use never develops or develops in a different direction than you expected and you end up rewriting or throwing away much of the framework -- or even worse, keeping and maintaining unused code. Let YAGNI (you aren't gonna need it) be your guide and delay refactoring to common libraries until you actually have a need.

Answer 2

There are a couple (at least) of different approaches here, and you could certainly use both. Firstly you could remove some common code in to a separate project and just call that code staticaly. This is pretty easy to do and I sometimes take this approach with simple helper functions that probably don't belong in a class in my main project - a good example would be a math library or something like that. The other approach is to extract common functionality in to a class or interface which you then inherit and extend. Depending on what code you are looking to reuse you might use either (or both) of these approaches.

I suspect you will find it easier than you think. Try it with some simple code, set up a new project in the same solution, reference your library from your existing code and see how it goes. There is also no reason not to reference your shared project in multiple solutions either.

Having shared code libraries need not be a problem if the development gets handed off. For now you can have your 2 sites reference the same library (or libraries) which you maintain, but if and when you split the projects out to other teams you can give a copy of the shared code to each team.