🔸 TLDR
DRY (Don't Repeat Yourself) is a core software engineering principle that encourages eliminating duplicated logic by centralizing knowledge in one place, making code easier to maintain and evolve.
🔸 WHAT IS THE DRY PRINCIPLE?
DRY stands for Don't Repeat Yourself.
It means that every piece of knowledge in a system should have a single, authoritative representation.
In practice, this means avoiding duplicated logic, configuration, or data definitions across the codebase.
If something changes, you should only have to update it in one place.
🔸 WHY DRY MATTERS
Duplicated logic leads to many problems over time:
▪️ Bug fixes must be applied in multiple places
▪️ Code becomes harder to maintain
▪️ Inconsistencies appear between implementations
▪️ Refactoring becomes risky
▪️ Development speed slows down
Applying DRY helps keep software clean, maintainable, and scalable.
🔸 COMMON WAYS TO APPLY DRY
Developers use several techniques to remove duplication:
▪️ Extract reusable methods or functions
▪️ Create shared utilities or libraries
▪️ Use inheritance or composition
▪️ Centralize configuration and constants
▪️ Use templates or code generation
▪️ Reuse domain models and DTOs
Example:
Instead of repeating validation logic everywhere, create a reusable validator.
🔸 DRY DOES NOT MEAN “ZERO DUPLICATION”
A common mistake is over-engineering abstractions too early.
Sometimes a small duplication is acceptable until a pattern clearly emerges.
Remember:
▪️ ⚠️ Premature abstraction can hurt readability
▪️ Over-generic code becomes harder to understand
▪️ DRY should improve clarity, not reduce it
Good developers balance DRY with simplicity.
🔸 TAKEAWAYS
▪️ DRY means one source of truth for each piece of logic
▪️ Duplicate code increases maintenance cost
▪️ Reusable functions and components help enforce DRY
▪️ Avoid premature abstractions
▪️ Balance DRY with readability and simplicity
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