Composition Over Inheritance: A Deep Dive into Flexible Object-Oriented Design

In software engineering, the “Composition Over Inheritance” (CoI) principle is central to object-oriented design, promoting a preference for composing objects with simple, independent parts rather than relying on complex class hierarchies. This principle has significant implications for flexibility, adaptability, and maintainability in code design, particularly within large and evolving codebases.

Understanding Composition and Inheritance

Composition: The “Has-a” Relationship

Composition involves building functionality by assembling small, modular components, each with distinct responsibilities. This allows developers to create objects by combining individual, self-contained parts, rather than relying on an inflexible class hierarchy. Composition embodies a “has-a” relationship — for example, a Car object may "have a" Engine component, without needing to be a subclass of Engine.

Inheritance: The “Is-a” Relationship