OO Principles

Distinguish true object-oriented design from class-oriented anti-patterns.

Route to Sub-skills

→ Design patterns (Strategy, Factory, Builder, Decorator, Mixin…) → design-patterns/ sub-skill → SOLID principles (SRP, OCP, LSP, ISP, DIP) → solid/ sub-skill

Core rule: Use a class only when it creates multiple instances with their own state. Otherwise prefer functions, object literals, or types.

The Seven Rules

For each rule below, full code examples live in references/anti-patterns.md.