Flet app workflow

Flet App Workflow

You are guiding the user through building a Flet declarative app step by step. Follow these 5 phases in order.

Before starting, confirm the app's purpose and target platforms with the user.

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Phase 1: Requirements

Ask the user about:

1. App purpose — What does the app do?
2. Target platforms — Web, mobile (Android/iOS), desktop (macOS/Windows/Linux)?
3. Pages needed — List the main screens/pages
4. External services — Any Flet extensions or APIs needed?
5. State shape — What data needs to be shared across pages?

Summarize the requirements before proceeding.

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Phase 2: Project Setup

For non-trivial apps, use the Clean Architecture layout (mirrors Flutter's lib/ convention, validated in production Flet apps). For 1–2-page prototypes, use the flat fallback below.

Clean Architecture (recommended)

my_app/
├── assets/                    # fonts/, icons/, images/
├── config.py                  # Project-root config
├── pyproject.toml             # [tool.flet.app] path = "src"
├── tests/                     # conftest.py, unit/, widget/, integration/
└── src/
    ├── main.py                # ft.run(create_app, assets_dir="assets")
    ├── app.py                 # create_app(page): theme, DI, page.render_views(...)
    ├── core/                  # constants.py, enums.py, exceptions.py, logger.py
    ├── data/                  # sources/, models/, repositories/
    ├── domain/                # entities/, repositories/, services/, usecases/
    ├── presentation/          # components/, pages/, navigation/, themes/, hooks/, state_management/
    ├── services/              # api_service.py, storage_service.py, ...
    └── utils/                 # validators.py, text_utils.py, ...

Flat (prototype / very small app)

my_app/
├── pyproject.toml          # [tool.flet.app] path = "src"
└── src/
    ├── main.py
    ├── config.py
    ├── state.py
    ├── context.py
    ├── components/
    │   └── __init__.py
    └── pages/
        └── __init__.py

1. Create pyproject.toml with Flet dependency and [tool.flet.app] path = "src"
2. Create state.py (or src/presentation/state_management/global_providers.py in the layered layout) with @ft.observable @dataclass AppState based on requirements
3. Create context.py (or co-locate in state_management/) with AppContext and AppCtx = ft.create_context(None)
4. Create config.py at project root (or src/core/constants.py for code-level constants) with app configuration and navigation defaults

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Phase 3: UI & Pages

For each page identified in Phase 1:

1. Create a @ft.component function in pages/<name>.py
2. Use ft.use_context(AppCtx) to access state and services
3. Use ft.use_state() for local form fields
4. Implement async handlers with try/except
5. Register in pages/__init__.py PAGE_BUILDERS dict

Create reusable components in components/:

• Navigation drawer (if multi-page)
• Log viewer, status bar, or other shared UI

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Phase 4: Logic & State

1. Wire up main.py:
   • Create state outside components
   • Initialize services with event handlers
   • Add services to page.services
   • Call page.render_views(App, state, ...services)
2. Implement the App root component:
   • Create AppContext with state + services
   • Build ft.View with AppBar, drawer, and PageContent
   • Use view_ref pattern for drawer
   • Provide context via AppCtx(ctx, build_view)
3. Implement PageContent component:
   • Read state.current_page from context
   • Render corresponding page from PAGE_BUILDERS

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Phase 5: Polish & Test

1. Test locally: flet run src or cd to project root and flet run
2. Add theming: page.theme = ft.Theme(color_scheme_seed=ft.Colors.BLUE)
3. Add responsive layout: Use ft.ResponsiveRow or breakpoint-based layouts
4. Error handling: Wrap service calls in try/except
5. Build for target platforms: flet build web, flet build apk, etc.

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Reminders

• Always use ft.run(main) — never ft.app()
• Always use declarative mode — no page.add() or page.update()
• @ft.observable BEFORE @dataclass (order matters)
• ft.use_state for form fields, @ft.observable for shared state
• Factory function for handlers in loops
• cleanup= parameter in use_effect, not return value