# Elct9620 AI Coding Skills Design Patterns

> Related Skills

- Skill: `tomevault-io/elct9620-ai-coding-skills-design-patterns` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/elct9620-ai-coding-skills-design-patterns`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/elct9620-ai-coding-skills-design-patterns/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/elct9620-ai-coding-skills-design-patterns

---


## Related Skills

- Modeling business concepts (Entity, Value Object)? → Use **domain-modeling** instead
- Restructuring existing code toward a pattern? → Use **refactoring** for safe migration steps
- Deciding if a pattern is even needed (YAGNI)? → Use **principles** to evaluate first

## Applicability Rubric

| Condition | Pass | Fail |
|-----------|------|------|
| Multi-component change | Feature affects multiple components | Single component change |
| Recognizable problem | Matches known design problem | Unique/novel problem |
| Flexibility needed | Requires extensible solution | Fixed requirements |
| Recurring challenge | Solving common design issue | One-off implementation |

**Apply when**: Any condition passes

## Core Principles

### Pattern Selection Process

```
1. Identify the problem
   ↓
2. Match problem to pattern category
   ↓
3. Evaluate pattern candidates
   ↓
4. Consider trade-offs
   ↓
5. Apply pattern minimally
```

### Pattern Categories

| Category | Purpose | Common Patterns |
|----------|---------|-----------------|
| Creational | Object creation | Factory, Builder, Singleton |
| Structural | Object composition | Adapter, Decorator, Facade |
| Behavioral | Object interaction | Strategy, Observer, Command |

## Pattern Quick Reference

| Category | Pattern | Use When | Example |
|----------|---------|----------|---------|
| Creational | Factory Method | Object creation varies by context | `createLogger(type)` |
| Creational | Builder | Complex object with many optional parts | Fluent configuration |
| Creational | Singleton | Single instance needed globally | Configuration manager |
| Structural | Adapter | Interface incompatibility | Wrap legacy API |
| Structural | Decorator | Add behavior dynamically | Logging wrapper |
| Structural | Facade | Simplify complex subsystem | Unified API client |
| Structural | Composite | Tree structures | UI components |
| Behavioral | Strategy | Algorithm varies at runtime | Payment methods |
| Behavioral | Observer | One-to-many notifications | Event system |
| Behavioral | Command | Encapsulate operations | Undo/redo actions |
| Behavioral | State | Behavior changes with state | Order status |

## Completion Rubric

### Before Applying

| Criterion | Pass | Fail |
|-----------|------|------|
| Problem identification | Problem clearly defined | Vague problem statement |
| Real need | Solves actual problem | Hypothetical/speculative |
| Simpler alternatives | Considered simpler options first | Jumped to pattern |
| Team familiarity | Team understands pattern | Pattern is obscure |

### During Implementation

| Criterion | Pass | Fail |
|-----------|------|------|
| Minimal application | Pattern applied minimally | Over-applied |
| Clear naming | Names reflect pattern intent | Generic/unclear names |
| Intent preservation | Pattern intent maintained | Pattern misused |
| Appropriate complexity | Complexity justified | Over-engineered |

### After Implementation

| Criterion | Pass | Fail |
|-----------|------|------|
| Flexibility gained | Code more flexible | Same or less flexible |
| Documented | Pattern documented if not obvious | Undocumented complexity |
| Tested | Tests cover pattern behavior | Pattern untested |

## Anti-Pattern Warning

**Pattern Fever**: Applying patterns everywhere

Signs:
- Patterns for trivial problems
- Multiple patterns where one suffices
- Code harder to understand than before

Cure: YAGNI - Use patterns only when they solve real problems

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