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Design Pattern Dangers

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Design Patterns and Domain Driven Design are two of the most dangerous books a new developer can read.

The books themselves are not bad. They offer standardized names for common programming practices, which has made communication a lot easier for everyone. Sometimes you will see that a pattern is merely a new name for something you may have already invented. Perhaps what you were calling a “builder” they call a “factory”. If you use the standard names, communication will be easier.

The problem is: both books are highly prescriptive. Highly prescriptive books discourage critical thinking if the reader lacks sufficient context.

both books are highly prescriptive

When an author says “I’ve done this, and it was a great silver bullet!”, they are prescribing a set of patterns that worked in a very specific context. The careful thinker can deconstruct the prescription. The most important part is when to do the pattern, not how to do it. Experienced programmers can mentally apply the patterns to situations they have seen before. They can consider the ramifications of any change in the context of their previous projects.

the most important part is when to do the pattern, not how

Unfortunately, as new developers, we’ve seen very few previous projects. We’ve not already invented these concepts. The allure of a silver bullet is so tempting that we get “pattern madness”.

Pattern madness? You know the signs. Every new line of code must be in service of a new pattern. We write patterns in places they do not belong: solutions looking for problems.

We can easily counter pattern madness. Never attempt to apply a pattern you have only read about, only rename existing places that already implement a pattern. This inversion is much more useful. You become a sleuth: searching for places the pattern already exists. Your code reading, working memory, and pattern recognition skills will all improve.

Not every house needs an elevator

Do not try to force every pattern into a codebase. Many codebases might only have one or two places where a pattern would solve a problem. Some codebases might not need a given pattern at all. Don’t worry when this happens, it is not a sign you have bad code or a bad architecture. As a metaphor, “not every house needs an elevator.”

steve shogren

software developer, manager, author, speaker

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