Data Layer

Goal

This snapshot advances Cobblecart Market by teaching you to model categories and products with migrations and seeds.

Every numbered folder is a complete app. Run this stage independently, then compare it with the previous folder.

Prerequisites

Use Ruby 3.2+, Bundler, Node.js 20+, and Docker for Postgres stages.

Port 3010 must be free. Copy .env.example before database stages.

• Ruby and Bundler
• Node.js and npm
• Docker from part 4 onward

Concepts

Each snapshot uses an isolated cobble_NN database so stages stay independent.

Turbo keeps interactive UI on the server; Tailwind styles the storefront; Active Record owns persistence and authorization checks.

Walkthrough

Migrate Category and Product tables, relate them, and seed Ada, Grace, and a starter catalog.

Read the example, then open the matching snapshot. The repository includes validation, CSRF, and the surrounding structure.

create_table :products do |t|
  t.references :user, null: false, foreign_key: true
  t.references :category, null: false
  t.string :name, null: false
  t.string :slug, null: false
  t.integer :price_cents, null: false
  t.integer :stock, default: 0
end

Run and verify

Enter 04-Data-Layer, bundle install, copy .env.example, migrate, seed, and boot Puma on port 3010.

Open http://127.0.0.1:3010. From data lessons onward, Ada and Grace use password123.

docker compose up -d
git clone https://github.com/michaeldunga1/fcc-rails-ecommerce.git
cd fcc-rails-ecommerce/04-Data-Layer
bundle install
npm install
cp .env.example .env
bin/rails db:prepare
bin/rails server -b 0.0.0.0 -p 3010

Troubleshooting

Connection refused usually means Docker is down or the database name does not match this folder's index.

For database failures, confirm Docker and the cobble_NN name. Never commit .env, vendor/bundle, or node_modules.

• Read the first exception first
• Rebuild assets after Tailwind class changes
• Never commit secrets

Try this

Add a nullable sku column through a new migration.

Test a happy path and one invalid or unauthorized request.

• Make one small change
• Test it in the browser
• Compare with the next snapshot only after it works