Chapter 21 Conclusion

This book is about one thing: complexity. Dealing with complexity is the most important challenge in software design. It is what makes systems hard to build and maintain, and it often makes them slow as well. Over the course of the book I have tried to describe the root causes that lead to complexity, such as dependencies and obscurity. I have discussed red flags that can help you identify unnecessary complexity, such as information leakage, unneeded error conditions, or names that are too generic. I have presented some general ideas you can use to create simpler software systems, such as striving for classes that are deep and generic, defining errors out of existence, and separating interface documentation from implementation documentation. And, finally, I have discussed the investment mindset needed to produce simple designs.

The downside of all these suggestions is that they create extra work in the early stages of a project. Furthermore, if you aren’t used to thinking about design issues, then you will slow down even more while you learn good design techniques. If the only thing that matters to you is making your current code work as soon as possible, then thinking about design will seem like drudge work that is getting in the way of your real goal.

On the other hand, if good design is an important goal for you, then the ideas in this book should make programming more fun. Design is a fascinating puzzle: how can a particular problem be solved with the simplest possible structure? It’s fun to explore different approaches, and it’s a great feeling to discover a solution that is both simple and powerful. A clean, simple, and obvious design is a beautiful thing.

Furthermore, the investments you make in good design will pay off quickly. The modules you defined carefully at the beginning of a project will save you time later as you reuse them over and over. The clear documentation that you wrote six months ago will save you time when you return to the code to add a new feature. The time you spent honing your design skills will also pay for itself: as your skills and experience grow, you will find that you can produce good designs more and more quickly. Good design doesn’t really take much longer than quick-and-dirty design, once you know how.

The reward for being a good designer is that you get to spend a larger fraction of your time in the design phase, which is fun. Poor designers spend most of their time chasing bugs in complicated and brittle code. If you improve your design skills, not only will you produce higher quality software more quickly, but the software development process will be more enjoyable.