Data Layer

Goal

This snapshot advances Junction Almanac by teaching you to persist users and posts with PostgreSQL and Active Record.

Every numbered folder is a complete Rails application. Run this stage independently, then compare it with the previous snapshot to isolate the new responsibility.

Prerequisites

Use Ruby 3.1 or newer, Bundler, PostgreSQL through Docker, and a terminal. Basic Ruby, HTML, and SQL vocabulary will make the framework conventions easier to recognize.

The app listens on port 3000. PostgreSQL is exposed on host port 5434, and every snapshot names a different database so lesson data never leaks between stages.

• Ruby and Bundler
• Docker with Compose
• A code editor and terminal

Concepts

Migrations version the schema, models declare relationships and validation, and Active Record turns relational rows into Ruby objects without removing database constraints.

Keep the Rails request path visible: the router selects a controller action, Active Record handles data rules, and an ERB view renders the response inside the shared layout.

Walkthrough

Create users with password digests, connect posts through a foreign key, add deterministic ordering indexes, migrate, and seed Ada and Grace.

Read the focused example, then inspect the matching repository snapshot for the surrounding configuration, validation, failure paths, and accessible markup.

class User < ApplicationRecord
  has_secure_password
  has_many :posts, dependent: :destroy
end

class Post < ApplicationRecord
  belongs_to :user
end

Run and verify

Enter 04-Data-Layer, install its bundle, prepare its database when this stage uses one, and start Rails on port 3000.

Open http://localhost:3000. Keep the server log visible so you can connect each browser action to its route, SQL query, rendered view, redirect, or validation error.

git clone https://github.com/michaeldunga1/fcc-rails-blog.git
cd fcc-rails-blog/04-Data-Layer
docker compose -f ../docker-compose.yml up -d
bundle install
bin/rails db:prepare db:seed
bin/rails server -p 3000

Troubleshooting

Authentication requires the bcrypt gem and a column named password_digest. Foreign-key failures reveal missing or invalid authors.

If Rails reports a missing table, run bin/rails db:prepare db:seed in the current snapshot. Connection failures usually mean PostgreSQL is stopped or port 5434 is already occupied.

• Read the first exception first
• Confirm the current numbered folder
• Never commit secrets or config/master.key

Try this

Open bin/rails console, query both users, and create a validated post.

Test one successful request and one invalid or unauthorized request. A production-minded Rails app must preserve data rules even when someone bypasses the visible links and submits a direct request.

• Make one focused change
• Verify it in the browser
• Move on only after the checkpoint works