m09-domain
CRITICAL: Use for domain modeling. Triggers: domain model, DDD, domain-driven design, entity, value object, aggregate, repository pattern, business rules, validation, invariant, 领域模型, 领域驱动设计, 业务规则
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/actionbook/rust-skills --skill m09-domain- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads m09-domain automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Domain Modeling
Layer 2: Design Choices
Core Question
What is this concept's role in the domain?
Before modeling in code, understand:
- Is it an Entity (identity matters) or Value Object (interchangeable)?
- What invariants must be maintained?
- Where are the aggregate boundaries?
Domain Concept → Rust Pattern
| Domain Concept | Rust Pattern | Ownership Implication |
|---|---|---|
| Entity | struct + Id | Owned, unique identity |
| Value Object | struct + Clone/Copy | Shareable, immutable |
| Aggregate Root | struct owns children | Clear ownership tree |
| Repository | trait | Abstracts persistence |
| Domain Event | enum | Captures state changes |
| Service | impl block / free fn | Stateless operations |
Thinking Prompt
Before creating a domain type:
-
What's the concept's identity?
- Needs unique identity → Entity (Id field)
- Interchangeable by value → Value Object (Clone/Copy)
-
What invariants must hold?
- Always valid → private fields + validated constructor
- Transition rules → type state pattern
-
Who owns this data?
- Single owner (parent) → owned field
- Shared reference → Arc/Rc
- Weak reference → Weak
Trace Up ↑
To domain constraints (Layer 3):
"How should I model a Transaction?"
↑ Ask: What domain rules govern transactions?
↑ Check: domain-fintech (audit, precision requirements)
↑ Check: Business stakeholders (what invariants?)
| Design Question | Trace To | Ask |
|---|---|---|
| Entity vs Value Object | domain-* | What makes two instances "the same"? |
| Aggregate boundaries | domain-* | What must be consistent together? |
| Validation rules | domain-* | What business rules apply? |
Trace Down ↓
To implementation (Layer 1):
"Model as Entity"
↓ m01-ownership: Owned, unique
↓ m05-type-driven: Newtype for Id
"Model as Value Object"
↓ m01-ownership: Clone/Copy OK
↓ m05-type-driven: Validate at construction
"Model as Aggregate"
↓ m01-ownership: Parent owns children
↓ m02-resource: Consider Rc for shared within aggregate
Quick Reference
| DDD Concept | Rust Pattern | Example |
|---|---|---|
| Value Object | Newtype | struct Email(String); |
| Entity | Struct + ID | struct User { id: UserId, ... } |
| Aggregate | Module boundary | mod order { ... } |
| Repository | Trait | trait UserRepo { fn find(...) } |
| Domain Event | Enum | enum OrderEvent { Created, ... } |
Pattern Templates
Value Object
struct Email(String);
impl Email {
pub fn new(s: &str) -> Result<Self, ValidationError> {
validate_email(s)?;
Ok(Self(s.to_string()))
}
}
Entity
struct UserId(Uuid);
struct User {
id: UserId,
email: Email,
// ... other fields
}
impl PartialEq for User {
fn eq(&self, other: &Self) -> bool {
self.id == other.id // Identity equality
}
}
Aggregate
mod order {
pub struct Order {
id: OrderId,
items: Vec<OrderItem>, // Owned children
// ...
}
impl Order {
pub fn add_item(&mut self, item: OrderItem) {
// Enforce aggregate invariants
}
}
}
Common Mistakes
| Mistake | Why Wrong | Better |
|---|---|---|
| Primitive obsession | No type safety | Newtype wrappers |
| Public fields with invariants | Invariants violated | Private + accessor |
| Leaked aggregate internals | Broken encapsulation | Methods on root |
| String for semantic types | No validation | Validated newtype |
Related Skills
| When | See |
|---|---|
| Type-driven implementation | m05-type-driven |
| Ownership for aggregates | m01-ownership |
| Domain error handling | m13-domain-error |
| Specific domain rules | domain-* |
FAQ
What does the m09-domain skill do?
CRITICAL: Use for domain modeling. Triggers: domain model, DDD, domain-driven design, entity, value object, aggregate, repository pattern, business rules, validation, invariant, 领域模型, 领域驱动设计, 业务规则
How do I install m09-domain?
Run npx skills add https://github.com/actionbook/rust-skills --skill m09-domain in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/m09-domain/ (personal) or .claude/skills/m09-domain/ (project).
Which AI agents can use m09-domain?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is m09-domain safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains m09-domain?
It is published by actionbook in actionbook/rust-skills. It has 3,341 recorded installs.
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