flutter-state-management

Goal

Implements robust state management and architectural patterns in Flutter applications using Unidirectional Data Flow (UDF) and the Model-View-ViewModel (MVVM) design pattern. Evaluates state complexity to differentiate between ephemeral (local) state and app (shared) state, applying the appropriate mechanisms (setState, ChangeNotifier, or the provider package). Ensures that the UI remains a pure function of immutable state and that the data layer acts as the Single Source of Truth (SSOT).

Instructions

1. Analyze State Requirements (Decision Logic)

Evaluate the data requirements of the feature to determine the appropriate state management approach. Use the following decision tree:

• Does the state only affect a single widget and its immediate children? (e.g., current page in a PageView, animation progress, local form input)
  • Yes: Use Ephemeral State (StatefulWidget + setState).
• Does the state need to be accessed by multiple unrelated widgets, or persist across different screens/sessions? (e.g., user authentication, shopping cart, global settings)
  • Yes: Use App State (MVVM with ChangeNotifier + provider).

STOP AND ASK THE USER: If the scope of the state (ephemeral vs. app-wide) is ambiguous based on the provided requirements, pause and ask the user to clarify the intended scope and lifecycle of the data.

2. Implement Ephemeral State (If Applicable)

For local UI state, use a StatefulWidget. Ensure that setState() is called immediately when the internal state is modified to mark the widget as dirty and schedule a rebuild.