Rails Service Object Patterns

Patterns for extracting and organizing business logic in Rails applications.

When This Skill Applies

• Extracting complex logic from controllers/models into service objects
• Implementing command/query separation patterns
• Handling multi-step business processes
• Designing result objects and error handling
• Organizing the app/services directory

Core Principles

Single Responsibility

Each service should do one thing well:

• Name services with verb + noun: CreateOrder, SendEmail, ProcessPayment
• Keep services focused and composable
• One public method (typically call or perform)

Dependency Injection

Make services testable and flexible:

class NotificationService
  def initialize(mailer: UserMailer, sms_client: TwilioClient.new)
    @mailer = mailer
    @sms_client = sms_client
  end
end

Service Patterns

See patterns.md for detailed implementations of:

• Basic Service Pattern
• Result Object Pattern
• Form Objects
• Query Objects
• Policy Objects

Quick Reference

Testing Services

RSpec.describe CreateOrder do
  let(:user) { create(:user) }
  let(:service) { described_class.new(user, cart_items) }

  describe '#call' do
    it 'creates an order' do
      expect { service.call }.to change { Order.count }.by(1)
    end

    context 'when payment fails' do
      before { allow(PaymentProcessor).to receive(:charge).and_raise(PaymentError) }

      it 'rolls back the transaction' do
        expect { service.call }.not_to change { Order.count }
      end
    end
  end
end

Related Documentation

• patterns.md - Detailed service patterns with examples