flutter-architecting-apps

Structure a Flutter app into three layers: a UI layer with lean widgets and view models, an optional logic layer with use cases, and a data layer with repositories and services. Each layer only communicates with the layer directly adjacent to it.

A service is a stateless class that wraps an external data source like an HTTP API or local database. A repository consumes services, acts as the single source of truth, and handles caching, offline sync, and transformation into domain models.

Add a logic layer with use cases or interactors only when the app has complex client-side business logic orchestrating multiple repositories. For standard CRUD apps, omit it and let view models call repositories directly.

Yes, the view model pattern uses ChangeNotifier with notifyListeners to expose immutable state, and widgets bind via ListenableBuilder. This integrates naturally with Provider for dependency injection across the widget tree.

For very small apps or prototypes, the full three-layer structure adds boilerplate without benefit. The guidance recommends omitting the logic layer for simple CRUD apps and keeping only UI and data layers.