# composition-over-inheritance

> Prefer composition (has-a) over inheritance (is-a) Use when designing system architecture. Architecture category skill.

- Author: OmniaffixDave
- Repository: OmniaffixDave/SessionGuardian
- Version: 20260205125233
- Stars: 0
- Forks: 1
- Last Updated: 2026-02-08
- Source: https://github.com/OmniaffixDave/SessionGuardian
- Web: https://mule.run/skillshub/@@OmniaffixDave/SessionGuardian~composition-over-inheritance:20260205125233

---

---
name: composition-over-inheritance
description: Prefer composition (has-a) over inheritance (is-a) Use when designing system architecture. Architecture category skill.
metadata:
  category: Architecture
  priority: medium
  is-built-in: true
  session-guardian-id: builtin_composition_over_inheritance
---

# Composition Over Inheritance

Prefer composition (has-a) over inheritance (is-a). Inheritance creates tight coupling and fragile base class problems. Compose objects from smaller, focused pieces. Use interfaces to define contracts. JavaScript/TypeScript mixins or object composition enable flexible code reuse without deep hierarchies. Reserve inheritance for true "is-a" relationships with shared behavior.