Data Layer

Goal

This snapshot advances Solstice Ledger by teaching you to persist authors and posts with Ecto and PostgreSQL.

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

Prerequisites

Use Elixir 1.15+, Mix, and Docker for Postgres stages.

Port 4001 must be free. Copy .env.example before starting database stages.

• Elixir and Mix
• A code editor and terminal
• Docker from part 4 onward

Concepts

Ecto schemas map tables. Each snapshot uses its own solstice database.

Keep controllers thin: plugs prepare requests, contexts enforce rules, and HEEx escapes output by default.

Walkthrough

Configure DATABASE_URL, create schemas, seed Ada and Grace.

Read the example, then open the matching snapshot. The repository includes the surrounding setup and error handling.

Repo.all(from p in Post, order_by: [desc: p.inserted_at], preload: [:author])

Run and verify

Enter 04-Data-Layer, fetch deps, copy .env.example, and start Phoenix on port 4001.

Open http://127.0.0.1:4001. Watch the terminal for validation and database errors.

docker compose up -d
git clone https://github.com/michaeldunga1/fcc-phoenix-blog.git
cd fcc-phoenix-blog/04-Data-Layer
mix deps.get
cp .env.example .env
mix phx.server

Troubleshooting

Connection refused usually means Docker Postgres is stopped or the port is not 5438.

For database failures, confirm Docker and the solstice_NN name when applicable. Never commit .env or _build/deps secrets.

• Read the first error first
• Restart after environment changes
• Never commit secrets

Try this

Add a minimum title length check in the changeset.

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