A successful prototype often puts a network request, a loading spinner, and a list in the same widget. That is a useful starting point. The next challenge arrives when a second screen needs the same data, or a failed request must be retried without losing what the user entered.

Give each part a clear responsibility

Flutter's architecture guide separates the UI layer from the data layer. A view describes the interface; a view model prepares its state and responds to actions. Repositories coordinate application data, while services wrap external sources such as an API or local storage. These are responsibilities you can express with ordinary Dart classes.

Start with one complete feature

For a saved-articles feature, create a repository that exposes saved articles and accepts a save action. Let a view model expose loading, content, and recoverable failure states. The widget should display those states and pass button presses back. Keep the API response format behind the repository boundary so a backend rename does not force edits throughout the UI.

abstract interface class SavedArticlesRepository {
  Future<List<String>> loadTitles();
  Future<void> save(String articleId);
}

This deliberately small interface makes a useful seam for a fake repository in tests. In a real feature, replace title strings with a typed article model and describe failures explicitly. Avoid exposing a database row or HTTP response directly to the screen.

Add complexity when the problem demands it

A domain use case is valuable when several repositories participate in one decision or when important rules are reused. A one-line pass-through class for every operation is usually less useful. Before introducing a layer, describe the duplication or testing problem it removes.

Review the boundary, not the folder names

  • Can the screen be tested without a real network connection?
  • Is there one clear owner for shared data?
  • Can a failed save be shown without clearing the last successful result?
  • Would replacing the API client require changing widgets?

Try this on one feature before reorganizing the entire application. A small, working slice gives the team a pattern that is easier to evaluate than a large diagram.

Official reference: Flutter app architecture guide.