Modern Rails 8 Architecture Patterns
Architecture Decision Tree
Where should this code go?
|
+- View/display formatting? -> Presenter (@presenter-agent)
+- Complex business logic? -> Service Object (@service-agent)
+- Complex database query? -> Query Object (@query-agent)
+- Shared behavior across models? -> Concern (/rails-concern skill)
+- Authorization logic? -> Policy (@policy-agent)
+- Reusable UI with logic? -> ViewComponent (@viewcomponent-agent)
+- Async/background work? -> Job (@job-agent, /solid-queue-setup skill)
+- Complex form (multi-model)? -> Form Object (@form-agent)
+- Transactional email? -> Mailer (@mailer-agent)
+- Real-time/WebSocket? -> Channel (/action-cable-patterns skill)
+- Data validation only? -> Model (@model-agent)
+- HTTP request/response only? -> Controller (@controller-agent)
Layer Responsibilities
| Layer |
Responsibility |
Should NOT contain |
| Controller |
HTTP, params, response |
Business logic, queries |
| Model |
Data, validations, relations |
Display logic, HTTP |
| Service |
Business logic, orchestration |
HTTP, display logic |
| Query |
Complex database queries |
Business logic |
| Presenter |
View formatting, badges |
Business logic, queries |
| Policy |
Authorization rules |
Business logic |
| Component |
Reusable UI encapsulation |
Business logic |
| Job |
Async processing |
HTTP, display logic |
| Form |
Complex form handling |
Persistence logic |
| Mailer |
Email composition |
Business logic |
| Channel |
WebSocket communication |
Business logic |
When NOT to Abstract
| Situation |
Keep It Simple |
Don't Create |
| Simple CRUD (< 10 lines) |
Keep in controller |
Service object |
| Used only once |
Inline the code |
Abstraction |
| Simple query with 1-2 conditions |
Model scope |
Query object |
| Basic text formatting |
Helper method |
Presenter |
| Single model form |
form_with model: |
Form object |
| Simple partial without logic |
Partial |
ViewComponent |
When TO Abstract
| Signal |
Action |
| Same code in 3+ places |
Extract to concern/service |
| Controller action > 15 lines |
Extract to service |
| Model > 300 lines |
Extract concerns |
| Complex conditionals |
Extract to policy/service |
| Query joins 3+ tables |
Extract to query object |
| Form spans multiple models |
Extract to form object |
See /extraction-timing skill for detailed extraction guidance.
Core Patterns
Skinny Controllers
# GOOD: Thin controller delegates to service
class OrdersController < ApplicationController
def create
result = Orders::CreateService.call(user: current_user, params: order_params)
if result.success?
redirect_to result.data, notice: t(".success")
else
flash.now[:alert] = result.error
render :new, status: :unprocessable_entity
end
end
end
Result Objects for Services
All services return a consistent Result object:
Result = Data.define(:success, :data, :error) do
def success? = success
def failure? = !success
end
Multi-Tenancy by Default
# GOOD: Scoped through account
def index
@events = current_account.events.recent
end
Rails 8 Specific Features
| Feature |
Purpose |
Skill/Agent |
| Authentication |
has_secure_password generator |
/authentication-flow |
| Background Jobs |
Solid Queue (database-backed) |
/solid-queue-setup, @job-agent |
| Real-time |
Action Cable + Solid Cable |
/action-cable-patterns |
| Caching |
Solid Cache (database-backed) |
/caching-strategies |
| Assets |
Propshaft + Import Maps |
(built-in) |
| Deployment |
Kamal 2 + Thruster |
(built-in) |
Testing Strategy by Layer
| Layer |
Test Type |
Focus |
| Model |
Unit |
Validations, scopes, methods |
| Service |
Unit |
Business logic, edge cases |
| Query |
Unit |
Query results, tenant isolation |
| Presenter |
Unit |
Formatting, HTML output |
| Controller |
Request |
Integration, HTTP flow |
| Component |
Component |
Rendering, variants |
| Policy |
Unit |
Authorization rules |
| System |
E2E |
Critical user paths |
New Feature Checklist
- Model - Define data structure (@migration-agent, @model-agent)
- Policy - Add authorization rules (@policy-agent)
- Service - Create for complex logic (@service-agent)
- Query - Add for complex queries (@query-agent)
- Controller - Keep it thin (@controller-agent)
- Presenter - Format for display (@presenter-agent)
- Component - Build reusable UI (@viewcomponent-agent)
- Mailer - Add transactional emails (@mailer-agent)
- Job - Add background processing (@job-agent)
References
- See layer-interactions.md for layer communication patterns
- See service-patterns.md for service object patterns
- See query-patterns.md for query object patterns
- See error-handling.md for error handling strategies
- See testing-strategy.md for comprehensive testing
1---2name: rails-architecture3description: Guides modern Rails 8 code architecture decisions and patterns. Use when deciding where to put code, choosing between patterns (service objects vs concerns vs query objects), designing feature architecture, refactoring for better organization, or when user mentions architecture, code organization, design patterns, or layered design. WHEN NOT: Implementing specific patterns (use specialist agents like service-agent or query-agent), writing tests, or debugging runtime errors.4---56# Modern Rails 8 Architecture Patterns78## Architecture Decision Tree910```11Where should this code go?12|13+- View/display formatting? -> Presenter (@presenter-agent)14+- Complex business logic? -> Service Object (@service-agent)15+- Complex database query? -> Query Object (@query-agent)16+- Shared behavior across models? -> Concern (/rails-concern skill)17+- Authorization logic? -> Policy (@policy-agent)18+- Reusable UI with logic? -> ViewComponent (@viewcomponent-agent)19+- Async/background work? -> Job (@job-agent, /solid-queue-setup skill)20+- Complex form (multi-model)? -> Form Object (@form-agent)21+- Transactional email? -> Mailer (@mailer-agent)22+- Real-time/WebSocket? -> Channel (/action-cable-patterns skill)23+- Data validation only? -> Model (@model-agent)24+- HTTP request/response only? -> Controller (@controller-agent)25```2627## Layer Responsibilities2829| Layer | Responsibility | Should NOT contain |30|-------|---------------|-------------------|31| **Controller** | HTTP, params, response | Business logic, queries |32| **Model** | Data, validations, relations | Display logic, HTTP |33| **Service** | Business logic, orchestration | HTTP, display logic |34| **Query** | Complex database queries | Business logic |35| **Presenter** | View formatting, badges | Business logic, queries |36| **Policy** | Authorization rules | Business logic |37| **Component** | Reusable UI encapsulation | Business logic |38| **Job** | Async processing | HTTP, display logic |39| **Form** | Complex form handling | Persistence logic |40| **Mailer** | Email composition | Business logic |41| **Channel** | WebSocket communication | Business logic |4243## When NOT to Abstract4445| Situation | Keep It Simple | Don't Create |46|-----------|----------------|--------------|47| Simple CRUD (< 10 lines) | Keep in controller | Service object |48| Used only once | Inline the code | Abstraction |49| Simple query with 1-2 conditions | Model scope | Query object |50| Basic text formatting | Helper method | Presenter |51| Single model form | `form_with model:` | Form object |52| Simple partial without logic | Partial | ViewComponent |5354## When TO Abstract5556| Signal | Action |57|--------|--------|58| Same code in 3+ places | Extract to concern/service |59| Controller action > 15 lines | Extract to service |60| Model > 300 lines | Extract concerns |61| Complex conditionals | Extract to policy/service |62| Query joins 3+ tables | Extract to query object |63| Form spans multiple models | Extract to form object |6465See /extraction-timing skill for detailed extraction guidance.6667## Core Patterns6869### Skinny Controllers7071```ruby72# GOOD: Thin controller delegates to service73class OrdersController < ApplicationController74 def create75 result = Orders::CreateService.call(user: current_user, params: order_params)76 if result.success?77 redirect_to result.data, notice: t(".success")78 else79 flash.now[:alert] = result.error80 render :new, status: :unprocessable_entity81 end82 end83end84```8586### Result Objects for Services8788All services return a consistent Result object:8990```ruby91Result = Data.define(:success, :data, :error) do92 def success? = success93 def failure? = !success94end95```9697### Multi-Tenancy by Default9899```ruby100# GOOD: Scoped through account101def index102 @events = current_account.events.recent103end104```105106## Rails 8 Specific Features107108| Feature | Purpose | Skill/Agent |109|---------|---------|-------------|110| Authentication | `has_secure_password` generator | /authentication-flow |111| Background Jobs | Solid Queue (database-backed) | /solid-queue-setup, @job-agent |112| Real-time | Action Cable + Solid Cable | /action-cable-patterns |113| Caching | Solid Cache (database-backed) | /caching-strategies |114| Assets | Propshaft + Import Maps | (built-in) |115| Deployment | Kamal 2 + Thruster | (built-in) |116117## Testing Strategy by Layer118119| Layer | Test Type | Focus |120|-------|-----------|-------|121| Model | Unit | Validations, scopes, methods |122| Service | Unit | Business logic, edge cases |123| Query | Unit | Query results, tenant isolation |124| Presenter | Unit | Formatting, HTML output |125| Controller | Request | Integration, HTTP flow |126| Component | Component | Rendering, variants |127| Policy | Unit | Authorization rules |128| System | E2E | Critical user paths |129130## New Feature Checklist1311321. **Model** - Define data structure (@migration-agent, @model-agent)1332. **Policy** - Add authorization rules (@policy-agent)1343. **Service** - Create for complex logic (@service-agent)1354. **Query** - Add for complex queries (@query-agent)1365. **Controller** - Keep it thin (@controller-agent)1376. **Presenter** - Format for display (@presenter-agent)1387. **Component** - Build reusable UI (@viewcomponent-agent)1398. **Mailer** - Add transactional emails (@mailer-agent)1409. **Job** - Add background processing (@job-agent)141142## References143144- See [layer-interactions.md](references/layer-interactions.md) for layer communication patterns145- See [service-patterns.md](references/service-patterns.md) for service object patterns146- See [query-patterns.md](references/query-patterns.md) for query object patterns147- See [error-handling.md](references/error-handling.md) for error handling strategies148- See [testing-strategy.md](references/testing-strategy.md) for comprehensive testing
thibautbaissac