"Flutter Repository Pattern with Supabase: Full Guide"
Flutter repository pattern with Supabase: abstract contracts, error mapping with Result types, repository vs data source, caching, and offline unit tests.
Here's a mistake every Flutter developer makes with Supabase exactly once: calling Supabase.instance.client.from('notes')... directly inside a widget. It works — until you need to unit-test that widget, cache the data, or switch a query, and suddenly Supabase calls are smeared across forty files. The Flutter repository pattern with Supabase fixes this by putting one clean abstraction between your UI and your backend. This guide builds a complete, runnable notes repository in Flutter 3.x: the abstract contract, the Supabase implementation, error mapping with a Result type, a local cache as a second data source, and a unit test that never touches the network. Along the way we'll settle the #1 confusion in this space — repository vs data source. What you'll learn Repository vs data source: the difference, shown in code The abstract repository contract (your UI's API to the backend) A Supabase implementation with real queries Error mapping: turning PostgrestException into domain failures with a Result type One repository, two data sources: adding a local cache When you should NOT use a repository Unit-testing the repository with a mocked data source Flutter Repository Pattern with Supabase: The Complete Picture The repository pattern says: your UI should never know where data comes from. It talks to a repository — a plain Dart class with methods like getNotes() and createNote() . Behind that interface, the repository talks to data sources (Supabase, a local database, an in-memory cache) and returns entities (pure Dart objects), never raw database rows. Three payoffs: testability (mock the repository, test widgets without network), swappability (change the backend without touching UI), and a single place for data logic like caching and error…