“prefer duplication over the wrong abstraction”
- Programmer A sees duplication.
- Programmer A extracts duplication and gives it a name.This creates a new abstraction. It could be a new method, or perhaps even a new class.
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Programmer A replaces the duplication with the new abstraction.
Ah, the code is perfect. Programmer A trots happily away.
- Time passes.
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A new requirement appears for which the current abstraction is almost perfect.
- Programmer B gets tasked to implement this requirement.Programmer B feels honor-bound to retain the existing abstraction, but since isn’t exactly the same for every case, they alter the code to take a parameter, and then add logic to conditionally do the right thing based on the value of that parameter.
What was once a universal abstraction now behaves differently for different cases.
- Another new requirement arrives.
Programmer X.
Another additional parameter.
Another new conditional.
Loop until code becomes incomprehensible. - You appear in the story about here, and your life takes a dramatic turn for the worse.
https://www.sandimetz.com/blog/2016/1/20/the-wrong-abstraction