Characters App

Building & Running the Application

• The project relies on Swift Package Manager (SPM) for dependency management, meaning there are no extra steps needed for package installation.
• The app builds and runs smoothly on the simulator. However, if you're deploying to a physical device, you may need to adjust the Bundle ID.

Key Design Decisions and Assumptions:

1. Architectural Choices:

• The app follows the MVVM (Model-View-ViewModel) architecture pattern.
• Dependency injection is used for the service layer to promote testability and flexibility.
• The application takes advantage of modern concurrency features in Swift, such as async/await and Task.
• Combine and @Published are used to implement reactive programming in the app’s state management.

2. Handling Concurrency and State:

• Task is utilized to manage asynchronous tasks throughout the app.
• Network requests support cancellation to avoid redundant tasks or unnecessary fetches.
• The app maintains isLoading and error states, providing feedback to users regarding ongoing processes and failures.
• AsyncStream is employed to manage and react to changes in character status.

3. Service Layer Design:

• An abstract CharacterServiceInterface protocol has been created to define the service layer, enabling easier testing and mocking.
• The service layer is flexible and can be swapped or mocked with minimal changes, thanks to dependency injection.

Solutions to Key Challenges:

1. Challenge: Managing Concurrent Network Requests

Solution: Implemented a mechanism for canceling tasks

• To avoid multiple overlapping requests, fetchTask?.cancel() is used to stop previous network calls.
• The Task.checkCancellation() method is used to quickly exit canceled tasks.

2. Challenge: Handling Network Errors Gracefully

Solution: Integrated error and loading states into the view model

• The view model tracks error and isLoading states to manage UI updates based on request status.
• During development, errors are logged to the console (though this would be replaced with more sophisticated logging in production).

3. Challenge: Ensuring Testability of Components

Solution: Dependency injection to decouple components

• Services are injected into view models, making it easier to mock dependencies for unit tests.
• The app’s view models are designed with clear, isolated methods, ensuring they remain simple and easy to test.

Author:

• Piotr Salari