Inheritance vs. Composition: The OOP Battle

Inheritance vs Composition

The ultimate showdown in Object-Oriented Design. Learn why modern development favors building over inheriting.

account_tree Inheritance

Classes derive properties and behaviors from parent classes. Ideally used for strict hierarchical taxonomies (e.g., a "Dog" is an "Animal").

check_circle Great for code reuse in stable hierarchies.

cancel Fragile Base Class: Changes to parents break children.

cancel Rigid: Hard to share code between unrelated branches.

extension Composition

Objects are built by combining smaller, independent components. This is like building with Lego blocks (e.g., a "Car" has an "Engine").

check_circle Flexible: Mix and match capabilities easily.

check_circle Loose Coupling: Components are independent and testable.

warning Can require more boilerplate wiring code.

The Robot Factory

Try to build a Flying & Shooting Robot using both methods.

account_tree Class Hierarchy

Select a base class chain. You can only pick one path down the tree.

Root Class

Robot

Subclass (Movement)

Sub-Subclass (Combat)

smart_toy

directions_walk

flight flight

cyclone

flare

psychology

Robot

robot_factory.js

"text-blue-400">class Robot "text-yellow-600">{
  "text-yellow-400">constructor"text-gray-400">("text-gray-400">) "text-yellow-600">{ "text-red-300">this.energy = 100; "text-yellow-600">}
"text-yellow-600">}

Why Use Composition?

Feature	Inheritance	Composition
Relationship	IS-A	HAS-A
Flexibility	Low. Defined at compile/creation time.	High. Can change at runtime.
Coupling	Tight. Child depends on Parent details.	Loose. Components are independent.
Problem	Fragile Base Class, Explosion of subclasses.	More boilerplate code, harder to debug.

Real World Check

You are building a UI Library. You have a `Button`. You want a `Button` that has an Icon, and a `Button` that has a Loading Spinner, and a `Button` that has both.