DRY (Don't Repeat Yourself)

Overview

Every piece of knowledge must have a single, unambiguous representation in the system.

If you find yourself writing the same logic twice, extract it. Duplication is a bug waiting to happen.

When to Use

• Writing code similar to existing code
• Copy-pasting and modifying
• Making the same change in multiple files
• Validation logic repeated across forms
• Same calculations in different places

The Iron Rule