Checkpoint Module

Before proceeding, test your understanding:

1. What does MedusaService() do?

   MedusaService() is a service factory provided by Medusa that generates a service with CRUD methods (create, update, retrieve, list, delete) for your data model. It saves you from writing boilerplate code.

2. Why is the module name “brand” and not “brand-module”?

   Medusa uses camelCase naming for modules and automatically adds “Module” as a suffix when resolving dependencies. So “brand” becomes “brandModule” internally. Using “brand-module” would result in “brandModuleModule”.

3. What would happen if you forgot to run migrations?

   The brand table wouldn’t exist in your database, and any attempt to create or retrieve brands would fail with database errors like “relation ‘brand’ does not exist”.

4. Why do we need to export both the service AND the module from index.ts?

   Exporting the service makes it available for dependency injection in workflows and API routes.

Implementation Check

Let me verify your implementation. Please share the following:

1. Directory Structure

Run this command and share the output:

Expected structure:

2. Data Model

Show me your src/modules/brand/models/brand.ts file.

Key things to check:

• Not done: Uses model.define() with “brand” as first argument (lowercase, snake-case)
• Not done: Has id: model.id().primaryKey()
• Not done: Has name: model.text()
• Not done: File is exported as default

3. Service

Show me your src/modules/brand/service.ts file.

Key things to check:

• Not done: Uses MedusaService(Brand) (capital B for the model import)
• Not done: File is exported as default

4. Module Definition

Show me your src/modules/brand/index.ts file.

Key things to check:

• Not done: Exports BrandService from service.ts
• Not done: Uses Module() with name “brand” (lowercase)
• Not done: Exports module as default

5. Configuration

Show me the modules section of your medusa-config.ts.

Key things to check:

• Not done: Includes resolve: "./modules/brand"
• Not done: Has empty options: {}

6. Migrations

Run this command and share the output:

Expected output: Should show migration succeeded without errors.

7. Build

Run this command and share any errors:

Expected output: Build should succeed. If there are TypeScript errors, share them with me so we can debug together.

Common Issues

“Cannot find module ‘brand’”

Symptom: Error when running build or starting server

Cause: Module not registered in medusa-config.ts

Fix:

1. Open medusa-config.ts
2. Add to modules array:

   typescriptCopy

   {
     resolve: "./modules/brand",
     options: {},
   }

3. Restart dev server

“Module name must be camelCase”

Symptom: Error about module naming convention

Cause: Used “brand-module” or “brandModule” as module name

Fix: Change module name to just “brand” in index.ts:

Testing Checklist

Verify each of these steps:

• Not done: Migration succeeded without errors
• Not done: Build succeeds without TypeScript errors
• Not done: Module appears in medusa-config.ts modules array
• Not done: File structure matches expected pattern
• Not done: Data model uses correct DML syntax
• Not done: Service uses MedusaService factory
• Not done: Module exports service

Next Steps

Once this checkpoint passes:

1. Brand Module is created and working
2. Next: Create the Brand Workflow (Part 2 of Lesson 1)

The module provides the data layer. Now we’ll build the workflow to orchestrate brand creation with automatic rollback capabilities.

Ready to continue? Let me know when all checks pass, and we’ll move on to creating the workflow.