/learning-medusa

Checkpoint 1.1: Brand Module

This checkpoint verifies that you've successfully created the Brand Module with its data model, service, and migrations.

Verification Questions

Before proceeding, test your understanding:

1. What does MedusaService() do?

   <details> <summary>Answer</summary>

   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.

   </details>

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

   <details> <summary>Answer</summary>

   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".

   </details>

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

   <details> <summary>Answer</summary>

   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".

   </details>

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

   <details> <summary>Answer</summary>

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

   </details>

Implementation Check

Let me verify your implementation. Please share the following:

1. Directory Structure

Run this command and share the output:

ls -R src/modules/brand

Expected structure:

src/modules/brand:
index.ts  models  service.ts

src/modules/brand/models:
brand.ts

2. Data Model

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

Key things to check:

• Uses model.define() with "brand" as first argument (lowercase, snake-case)
• Has id: model.id().primaryKey()
• Has name: model.text()
• File is exported as default

3. Service

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

Key things to check:

• Uses MedusaService(Brand) (capital B for the model import)
• File is exported as default

4. Module Definition

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

Key things to check:

• Exports BrandService from service.ts
• Uses Module() with name "brand" (lowercase)
• Exports module as default

5. Configuration

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

Key things to check:

• Includes resolve: "./modules/brand"
• Has empty options: {}

6. Migrations

Run this command and share the output:

npx medusa db:migrate

Expected output: Should show migration succeeded without errors.

7. Build

Run this command and share any errors:

npm run build

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:

   {
     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:

export default Module("brand", {
  service: BrandService,
})

Testing Checklist

Verify each of these steps:

• Migration succeeded without errors
• Build succeeds without TypeScript errors
• Module appears in medusa-config.ts modules array
• File structure matches expected pattern
• Data model uses correct DML syntax
• Service uses MedusaService factory
• 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.