flutter-apply-architecture-best-practices

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.
• Repositories: Consume one or more Services. Transform raw API models into clean Domain Models. Handle caching, offline synchronization, and retry logic. Expose Domain Models to ViewModels.

Logic Layer (Domain - Optional)

• Use Cases: Implement this layer only if the application contains complex business logic that clutters the ViewModel, or if logic must be reused across multiple ViewModels. Extract this logic into dedicated Use Case (interactor) classes that sit between ViewModels and Repositories.

Project Structure

Organize the codebase using a hybrid approach: group UI components by feature, and group Data/Domain components by type.

lib/
├── data/
│   ├── models/         # API models
│   ├── repositories/   # Repository implementations
│   └── services/       # API clients, local storage wrappers
├── domain/
│   ├── models/         # Clean domain models
│   └── use_cases/      # Optional business logic classes
└── ui/
    ├── core/           # Shared widgets, themes, typography
    └── features/
        └── [feature_name]/
            ├── view_models/
            └── views/