Repository pattern in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main purpose of the Repository pattern in Flutter?

Choose the best explanation for why developers use the Repository pattern in Flutter apps.

A To separate data access logic from UI code, making the app easier to maintain and test.

B To directly connect UI widgets to the database without any middle layer.

C To combine all app logic into one class for faster development.

D To replace Flutter's built-in state management with a new system.

💡 Hint

Think about how to keep your UI code clean and easy to change.

The Repository pattern acts as a middleman between data sources and UI, helping keep code organized and testable.

❓ ui_behavior

intermediate

How does the Repository pattern affect UI updates in Flutter?

If you use a Repository to fetch data, what happens when the data changes?

A The UI automatically updates without any notification from the Repository.

B The UI never updates because the Repository blocks changes.

C The Repository directly changes UI widgets without rebuilding.

D The Repository notifies the UI, which then rebuilds to show updated data.

💡 Hint

Think about how Flutter knows when to redraw widgets.

Repositories usually notify listeners or use streams so UI can rebuild with fresh data.

❓ lifecycle

advanced

When should you dispose resources in a Repository in Flutter?

Consider a Repository that uses streams to fetch data. When is the best time to close these streams?

A Immediately after creating the Repository, before any data is fetched.

B Never, streams stay open for the app's entire lifetime.

C When the Repository is no longer needed, typically when the app or feature is closed.

D Only when the UI widget using the Repository is disposed, regardless of Repository lifecycle.

💡 Hint

Think about cleaning up to avoid memory leaks.

Closing streams when the Repository is disposed prevents resource leaks and unexpected behavior.

❓ navigation

advanced

How does the Repository pattern help with navigation decisions in Flutter apps?

If your app needs to decide which screen to show based on user data from a Repository, how should this be handled?

A The Repository directly calls Navigator methods to change screens.

B The UI listens to the Repository and navigates when data changes indicate a new screen is needed.

C Navigation logic is hardcoded in the UI without consulting the Repository.

D The Repository blocks navigation until the user manually refreshes the app.

💡 Hint

Think about separation of concerns between data and UI.

UI listens to Repository data changes and decides navigation, keeping Repository focused on data only.

🔧 Debug

expert

What error will this Flutter Repository code cause?

Consider this Dart code snippet for a Repository: class UserRepository { StreamController _controller = StreamController(); Stream get userStream => _controller.stream; void fetchUser() { _controller.add('User data'); } void dispose() { // Missing _controller.close() } } What problem will happen if dispose() is called without closing _controller?

A Memory leak and possible StreamSubscription errors because the stream is not closed.

B No problem; streams do not need to be closed in Dart.

C The app will crash immediately when fetchUser() is called.

D The UI will never receive any data from the stream.

💡 Hint

Think about resource cleanup for streams.

Not closing StreamControllers causes memory leaks and can cause errors when listeners remain active.