Beyond Legacy Code

Refactor to the Open-Closed

These are five words that changed my life. It’s a way to help get out of this rut of legacy code. Refactoring is changing the design without changing the external behavior. The Open-Closed Principle says software entities should be “open for extension but closed for modification.” In other words, strive to make adding any new feature a matter of adding new code and minimally changing existing code. Avoid changing existing code because that’s when new bugs are likely to be introduced.

Refactoring to the Open-Closed is a way to add features to software safely and cost-effectively. Always make every change in a two-step process. First, refactor the code you want to extend so that it can accommodate the new feature. ...