Let's move on to the YAGNI principle:
- Y: You
- A: Aren't
- G: Gonna
- N: Need
- I: It
YAGNI says you should only develop software that is needed today. This principle came from Extreme Programming (XP). See what Ron Jeffries, co-founder of XP, wrote in his blog:
"Always implement things when you actually need them, never when you just foresee that you need them."
Software engineers are sometimes tempted to develop functionality that they feel the customer will need in the future. It's been proven time and time again that this is not the most effective way to develop software. Consider the following scenarios:
- The functionality is never needed by the customer and so the code is never used.
- The business environment changes and the system has to be redesigned or replaced.
- The technology changes and the system has to be upgraded to use a new library, a new framework, or a new language.
The cheapest software is the one that you didn't write. You aren't gonna need it!