Clean Architecture layers in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the layer responsible for UI in Clean Architecture.

Flutter

class [1]Layer {
  void render() {
    print('Display UI');
  }
}

Drag options to blanks, or click blank then click option'

APresentation

BData

CDomain

DInfrastructure

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the Domain layer with the UI layer.

Using Data layer name for UI.

The Presentation layer handles the UI and user interaction in Clean Architecture.

2fill in blank

medium

Complete the code to define the layer that contains business rules in Clean Architecture.

Flutter

abstract class [1]Layer {
  void executeBusinessLogic();
}

Drag options to blanks, or click blank then click option'

AData

BDomain

CPresentation

DService

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing Domain with Data layer responsibilities.

Thinking Presentation layer holds business logic.

The Domain layer contains business rules and logic independent of UI or data sources.

3fill in blank

hard

Fix the error in the code by choosing the correct layer name for data handling.

Flutter

class [1]Layer {
  void fetchData() {
    print('Get data from API or DB');
  }
}

Drag options to blanks, or click blank then click option'

ADomain

BBusiness

CPresentation

DData

Attempts:

3 left

💡 Hint

Common Mistakes

Using Domain or Presentation layer for data fetching.

Naming the layer incorrectly as Business.

The Data layer manages data sources like APIs and databases in Clean Architecture.

4fill in blank

hard

Fill both blanks to complete the Flutter widget that uses the Presentation and Domain layers.

Flutter

class MyWidget extends StatelessWidget {
  final [1]Layer domainLayer;

  MyWidget(this.domainLayer);

  @override
  Widget build(BuildContext context) {
    return [2]();
  }
}

Drag options to blanks, or click blank then click option'

ADomain

BContainer

CPresentation

DScaffold

Attempts:

3 left

💡 Hint

Common Mistakes

Using Presentation as a type for domainLayer variable.

Using Container instead of Scaffold for UI.

The widget depends on the Domain layer for logic and uses Scaffold as the UI container in Presentation.

5fill in blank

hard

Fill all three blanks to complete the repository pattern connecting Domain and Data layers.

Flutter

abstract class [1]Repository {
  Future<String> fetchData();
}

class [2]RepositoryImpl implements [3]Repository {
  @override
  Future<String> fetchData() async {
    return 'Data from API';
  }
}

Drag options to blanks, or click blank then click option'

AUser

DProduct

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for interface and implementation.

Mixing Product and User names incorrectly.

The UserRepository interface in Domain is implemented by UserRepositoryImpl in Data layer to fetch data.

Practice

1. Which layer in Clean Architecture is responsible for handling the user interface in a Flutter app?

easy

A. Domain layer

B. Presentation layer

C. Data layer

D. Network layer

Solution

1. Step 1: Understand the role of each layer

   The Presentation layer manages UI elements and user interactions.

2. Step 2: Match the layer to UI responsibility

   Since UI is about what the user sees and interacts with, it belongs to the Presentation layer.

3. Final Answer:

   Presentation layer -> Option B

4. Quick Check:

   UI = Presentation layer [OK]

Hint: UI always belongs to Presentation layer [OK]

Common Mistakes:

• Confusing Domain layer with UI
• Thinking Data layer handles UI
• Assuming Network layer is part of UI

2. Which of the following is the correct way to describe the Domain layer in Clean Architecture?

easy

A. It contains business logic and rules.

B. It handles data storage and retrieval.

C. It manages UI components and widgets.

D. It deals with network requests and APIs.

Solution

1. Step 1: Identify the Domain layer's responsibility

   The Domain layer contains the core business logic and rules of the app.

2. Step 2: Eliminate incorrect options

   Data storage is Data layer, UI is Presentation, network is part of Data or external services.

3. Final Answer:

   It contains business logic and rules. -> Option A

4. Quick Check:

   Domain = Business logic [OK]

Hint: Domain layer = business rules and logic [OK]

Common Mistakes:

• Mixing Domain with Data layer
• Thinking Domain manages UI
• Confusing network tasks with Domain

3. Given the following Flutter app structure, which layer should contain the repository interface?

lib/
  presentation/
  domain/
    repositories/
  data/
    repositories_impl/

medium

A. Presentation layer

B. Data layer

C. Domain layer

D. UI layer

Solution

1. Step 1: Understand repository interface placement

   Repository interfaces define contracts for data access and belong in the Domain layer.

2. Step 2: Check the folder structure

   Domain layer has 'repositories' folder for interfaces; Data layer has 'repositories_impl' for implementations.

3. Final Answer:

   Domain layer -> Option C

4. Quick Check:

   Repository interface = Domain layer [OK]

Hint: Interfaces go in Domain, implementations in Data [OK]

Common Mistakes:

• Putting interfaces in Data layer
• Confusing UI layer with Presentation
• Ignoring folder naming conventions

4. In a Flutter app using Clean Architecture, a developer places API call code directly inside a widget class. What is the main problem with this approach?

medium

A. It violates the separation of concerns by mixing UI and data logic.

B. It improves app performance by reducing layers.

C. It follows Clean Architecture best practices.

D. It makes the Domain layer responsible for UI.

Solution

1. Step 1: Identify the problem with API calls in UI

   API calls belong in the Data layer, not in UI widgets.

2. Step 2: Understand separation of concerns

   Mixing UI and data logic breaks Clean Architecture principles, making code harder to maintain.

3. Final Answer:

   It violates the separation of concerns by mixing UI and data logic. -> Option A

4. Quick Check:

   UI should not contain data logic [OK]

Hint: Keep API calls out of UI widgets [OK]

Common Mistakes:

• Thinking mixing layers improves performance
• Assuming Domain layer handles UI
• Believing this is best practice

5. You want to add a new feature to your Flutter app that fetches user profiles from a remote server. According to Clean Architecture, where should you place the code that converts JSON data into Dart objects?

hard

A. In the Presentation layer inside widgets

B. In the Domain layer as part of business logic

C. Directly inside the main.dart file

D. In the Data layer within model or mapper classes

Solution

1. Step 1: Identify JSON conversion responsibility

   Converting JSON to Dart objects is a data transformation task, part of data handling.

2. Step 2: Match task to Clean Architecture layer

   Data layer handles data sources and transformations, so JSON parsing belongs here.

3. Step 3: Exclude other layers

   Presentation is UI only, Domain is business rules, main.dart is app entry point, not for data parsing.

4. Final Answer:

   In the Data layer within model or mapper classes -> Option D

5. Quick Check:

   JSON parsing = Data layer [OK]

Hint: Put JSON parsing in Data layer models/mappers [OK]

Common Mistakes:

• Parsing JSON in UI widgets
• Putting parsing in Domain layer logic
• Adding parsing code in main.dart