Describe a scenario where using a single ViewModel for a complex Activity or Fragment might lead to maintainability problems. How would you refactor the architecture to improve it?
Android interview question for Advanced practice.
Answer
A single ViewModel for a complex screen can become a monolithic, difficult-to-maintain class as the UI grows. If the screen has distinct sections with independent data and UI state, a single ViewModel will mix unrelated logic. For example, an e-commerce product details screen might display product information, customer reviews, and related items. Each section has its own data source and UI interactions. Refactoring: Separate the ViewModel into smaller, focused ViewModels, one for each section. Use a parent ViewModel to coordinate between these child ViewModels. This approach makes the code more modular, testable, and understandable. Consider using a mediator pattern to communicate between them, or using a shared ViewModel store if appropriate. Each child ViewModel will handle only its part of the UI state, making it easier to manage and change without impacting other sections. This modularity improves maintainability and allows parallel development.
Explanation
Modularizing ViewModels improves code reusability and simplifies testing.