open-closed-principle.md

Open-closed principle

A software module should be

• open to extension i.e. it should be possible to add new feature
• closed to modification i.e. the addition of new feature should cause little to no (preferable) changes to the existing code.

Implementation

Use abstract base classes or interfaces to define the form/shape of the module. Different implementations can then provide distinct but similar functionality. Some of the implementations could even be extended by subclasses to add additional fields and methods.