Architecting Flutter Applications

Contents

• Architectural Layers
• Project Structure
• Workflow: Implementing a New Feature
• Examples

Architectural Layers

Enforce strict Separation of Concerns by dividing the application into distinct layers. Never mix UI rendering with business logic or data fetching.

UI Layer (Presentation)

Implement the MVVM (Model-View-ViewModel) pattern to manage UI state and logic.

• Views: Write reusable, lean widgets. Restrict logic in Views to UI-specific operations (e.g., animations, layout constraints, simple routing). Pass all required data from the ViewModel.
• ViewModels: Manage UI state and handle user interactions. Extend ChangeNotifier (or use Listenable) to expose state. Expose immutable state snapshots to the View. Inject Repositories into ViewModels via the constructor.

Data Layer

Implement the Repository pattern to isolate data access logic and create a single source of truth.

• Services: Create stateless classes to wrap external APIs (HTTP clients, local databases, platform plugins). Return raw API models or Result wrappers.