Code Smells
I’ve been reading Agile Software Development: Principles, Patterns, and Practices, by Bob Martin, recently. One part I’ve really enjoyed is his discussion of “design smells - the odors of rotting software.” It’s interesting to hear about what causes software projects to go wrong, and think about how I can write code that avoids these problems. Bob talks about 7 problems that exhibit “rotting” software.
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Rigidity - The system is hard to change because every change forces many other changes to other parts of the system.
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Fragility - Changes cause the system to break in places that have no conceptual relationship to the part that was changed.
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Immobility - It is hard to disentangle the system into components that can be reused in other systems.
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Viscosity - Doing things right is harder than doing things wrong.
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Needless Complexity - The design contains infrastructure that adds no direct benefit.
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Needless Repetition - The design contains repeating structures that could be unified under a single abstraction.
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Opacity - It is hard to read and understand. It does not express its intent well.
From the projects I’ve worked on, I can easily see how adding more of any of these factors would make the code unfriendly to work with. I’ve also seen how keeping the SOLID principles in mind can help you avoid these code smells.
Another interesting part of this book so far is seeing how writing good code that’s easy to change and utilizes the SOLID design principles is so closely tied to being able to practice Agile software development effectively. I previously hadn’t made that connection between the short iterations and openness to changing requirements, and the need for code that is modular and easy to change. I had only seen good code design as a benefit to the actual act of writing code, but it’s also a huge benefit to the Agile business process.
I’ve really enjoyed this book so far. I think it has a lot of highly applicable material, so I’m looking forward to learning a lot as I finish reading.