Data Layer

Goal

This snapshot advances Circuit Daily by teaching you to persist authors and posts with TypeORM and PostgreSQL.

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

Prerequisites

Use Node.js 20+, npm, and a terminal. You should recognize TypeScript modules, decorators, and HTTP verbs.

Port 3001 must be free. Copy .env.example before starting database stages.

• Node.js and npm
• A code editor and terminal
• Docker from part 4 onward

Concepts

TypeORM entities map classes to tables. Each snapshot uses its own circuit database so stages stay independent.

Keep controllers thin: accept input, call services, render Handlebars views. Escape stays on by default in templates.

Walkthrough

Connect with DATABASE_URL, create User and Post entities, seed Ada and Grace, and list posts on the home page.

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

await this.posts.find({ relations: ['author'], order: { createdAt: 'DESC' } });

Run and verify

Enter 04-Data-Layer, install dependencies, copy .env.example when present, and start Nest on port 3001.

Open http://127.0.0.1:3001. Watch the terminal for validation and database errors.

docker compose up -d
git clone https://github.com/michaeldunga1/fcc-nestjs-blog.git
cd fcc-nestjs-blog/04-Data-Layer
npm install
cp .env.example .env
npm run start:dev

Troubleshooting

Connection refused usually means Docker Postgres is stopped or the port is not 5437.

Missing-module errors usually mean npm install ran in another snapshot. For Postgres failures, confirm Docker and the circuit_NN database name.

• Read the first error first
• Restart after environment changes
• Never commit .env or node_modules

Try this

Add a minimum title length check before insert.

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