Data Layer

Goal

This snapshot advances Wavelength Daily by teaching you to model profiles and posts in Supabase Postgres with RLS.

Each numbered folder is a complete app. Run it independently and compare adjacent snapshots to isolate the new responsibility.

Prerequisites

Use Node.js 20 or newer, npm, and a terminal. Basic TypeScript, HTML, and CSS familiarity will help.

The development server uses port 5173. Database snapshots also need Docker and the Supabase CLI.

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

Concepts

Migrations make schema changes repeatable; row-level security makes authorization part of every query.

SvelteKit keeps route UI, server loading, and form actions close together while preserving a clear browser/server boundary.

Walkthrough

Start Supabase, apply the migration, inspect Ada and Grace in Studio, and review public, owner, and storage policies.

Trace the example from request to rendered page, then inspect the complete matching snapshot for types, validation, and failure handling.

create policy "authors update own posts" on posts for update using (auth.uid() = author_id);

Run and verify

Enter 04-Data-Layer, install dependencies, and start the app. Supabase stages must start the local stack and copy the printed anon key into .env.

Open http://localhost:5173 and keep the terminal visible so browser actions can be matched to server errors.

git clone https://github.com/michaeldunga1/fcc-sveltekit-blog.git
cd fcc-sveltekit-blog/04-Data-Layer
npm install
npx supabase start
cp .env.example .env
npm run dev

Troubleshooting

If data is missing, run npx supabase db reset and inspect the migration before changing application code.

A missing package usually means npm install ran in another snapshot. After changing environment variables, restart the SvelteKit process.

• Read the first error first
• Check the current snapshot path
• Never commit .env or node_modules

Try this

Use Studio to verify a published story and a private draft.

Test one happy path and one invalid or unauthorized path before moving on.

• Make one focused change
• Verify it in the browser
• Compare with the next snapshot after it works