name: design-patterns description: Design pattern recommendations (creational, structural, behavioral). Use when designing an abstraction and a pattern must be chosen. metadata: version: "1.0.0"

neuron: design-patterns

• triggers_when: a design pattern must be chosen before implementing
• tier: T2
• budget: 400 tokens
• eval: pattern chosen with correct justification -> threshold 1
• reward: pheromone +1 if eval >= threshold

Procedure

1. Identify the need: create, compose or communicate objects.
2. Walk the decision tree (runtime type? incompatible interfaces? algorithm selection?).
3. Choose the pattern that solves the concrete need.
4. Discard anti-patterns (no Singleton if multiple instances, no Factory if new suffices).

Checklist

• [ ] Need classified (creational/structural/behavioral)
• [ ] First-choice pattern considered
• [ ] Alternative evaluated if it applies
• [ ] Anti-patterns discarded

Pitfalls

• Singleton for multi-instance services
• Adapter when simple delegation suffices
• State when a simple if/else is enough