Ddd Tactical Patterns

1---
2name: ddd-tactical-patterns
3description: Apply DDD tactical patterns in code using entities, value objects, aggregates, repositories, and domain events with explicit invariants.
4risk: safe
5source: self
6tags: [ddd, tactical, aggregates, value-objects, domain-events]
7---
8 
9# DDD Tactical Patterns
10 
11## Use this skill when
12 
13- Translating domain rules into code structures.
14- Designing aggregate boundaries and invariants.
15- Refactoring an anemic model into behavior-rich domain objects.
16- Defining repository contracts and domain event boundaries.
17 
18## Do not use this skill when
19 
20- You are still defining strategic boundaries.
21- The task is only API documentation or UI layout.
22- Full DDD complexity is not justified.
23 
24## Instructions
25 
261. Identify invariants first and design aggregates around them.
272. Model immutable value objects for validated concepts.
283. Keep domain behavior in domain objects, not controllers.
294. Emit domain events for meaningful state transitions.
305. Keep repositories at aggregate root boundaries.
31 
32If detailed checklists are needed, open `references/tactical-checklist.md`.
33 
34## Example
35 
36```typescript
37class Order {
38  private status: "draft" | "submitted" = "draft";
39 
40  submit(itemsCount: number): void {
41    if (itemsCount === 0) throw new Error("Order cannot be submitted empty");
42    if (this.status !== "draft") throw new Error("Order already submitted");
43    this.status = "submitted";
44  }
45}
46```
47 
48## Limitations
49 
50- This skill does not define deployment architecture.
51- It does not choose databases or transport protocols.
52- It should be paired with testing patterns for invariant coverage.
53