data-oriented-architecture

name	data-oriented-architecture
description	Apply when encountering switch/if-else dispatch on entity type, designing entity systems, or refactoring toward extensibility. Provides registry-based dispatch, capability composition, and infrastructure-first patterns. Complements solid-architecture.

Data-Oriented Architecture Patterns

When To Use This Skill

Activate this skill when:

• Encountering switch statements or if/else chains dispatching on entity/object type
• Designing systems with multiple variants of similar entities
• Refactoring code where adding new types requires changes in multiple locations
• Building plugin systems, handler registries, or factory patterns
• Noticing the "expression problem" (hard to add new types AND new operations)

Core Principle

Separate data from behavior, dispatch via registry.

Entity = Pure Data (what it IS) + type discriminator
Definition = Bundled Behavior (what it DOES)
Registry = Type → Definition mapping (HOW to dispatch)

Pattern 1: Registry-Based Polymorphism

Problem

Switch statements scattered throughout codebase:

// Scattered in rendering.ts
switch (entity.type) {
  case 'typeA': renderA(entity); break;
  case 'typeB': renderB(entity); break;
}

// Scattered in update.ts
switch (entity.type) {
  case 'typeA': updateA(entity); break;
  case 'typeB': updateB(entity); break;
}

// Adding new type = edit N files

Solution

Single registry bundling all type-specific behavior:

// definitions.ts - ONE location for all type-specific code
const DEFS: Record<EntityType, Definition> = {
  typeA: { render: renderA, update: updateA, ... },
  typeB: { render: renderB, update: updateB, ... },
};

// Consumers dispatch generically
DEFS[entity.type].render(entity, ctx);
DEFS[entity.type].update(entity, dt);

// Adding new type = ONE registry entry, ZERO consumer changes