# Class

> Class & OOP reference — inheritance, polymorphism, composition, SOLID principles, design patterns. Use when designing class hierarchies, refactoring object-oriented code, or learning OOP concepts.

- Skill: `bytesagain/class` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add bytesagain/class`
- Raw SKILL.md: https://api.skillmd.com/api/skills/bytesagain/class/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: bytesagain (https://skillmd.com/u/bytesagain)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/bytesagain/class

---


# Class — Object-Oriented Programming Reference

Quick-reference skill for OOP concepts, class design, SOLID principles, and common design patterns.

## When to Use

- Designing class hierarchies and choosing inheritance vs composition
- Applying SOLID principles to refactor code
- Understanding polymorphism, encapsulation, and abstraction
- Choosing the right design pattern for a problem
- Comparing OOP across languages (Java, Python, TypeScript, C++)

## Commands

### `intro`

```bash
scripts/script.sh intro
```

OOP fundamentals — classes, objects, the four pillars.

### `solid`

```bash
scripts/script.sh solid
```

SOLID principles — SRP, OCP, LSP, ISP, DIP explained with examples.

### `inheritance`

```bash
scripts/script.sh inheritance
```

Inheritance vs composition — when to use each, diamond problem, mixins.

### `patterns`

```bash
scripts/script.sh patterns
```

Essential design patterns — Factory, Strategy, Observer, Singleton, Builder.

### `access`

```bash
scripts/script.sh access
```

Access modifiers and encapsulation — public, private, protected across languages.

### `abstract`

```bash
scripts/script.sh abstract
```

Abstract classes, interfaces, and protocols — contracts and polymorphism.

### `pitfalls`

```bash
scripts/script.sh pitfalls
```

Common OOP pitfalls — God class, deep hierarchies, over-engineering.

### `comparison`

```bash
scripts/script.sh comparison
```

OOP across languages — Java, Python, TypeScript, Go, Rust.

### `help`

```bash
scripts/script.sh help
```

### `version`

```bash
scripts/script.sh version
```

## Configuration

| Variable | Description |
|----------|-------------|
| `CLASS_DIR` | Data directory (default: ~/.class/) |

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