MVC (Model-View-Controller)

MVC separates the application into three interconnected components, aiming to decouple the presentation layer from the data and logic.

• Model: The Model represents the data and business logic of the application. It is responsible for fetching, storing, and processing data, often interacting with a database or network APIs.
• View: The View is responsible for the presentation layer, displaying the data to the user and forwarding user interactions (e.g., clicks, gestures) to the Controller. Examples in Android include Activities, Fragments, or custom views.
• Controller: The Controller serves as an intermediary between the Model and View. It handles user inputs, coordinates interactions, and ensures the View reflects changes in the Model.

MVP (Model-View-Presenter)

MVP enhances separation of concerns compared to MVC by clearly defining roles and decoupling the View and Presenter. It is a preferred design pattern for Android applications due to improved testability and maintainability. The Presenter handles UI logic and can be tested independently of the Android framework, which simplifies unit testing.

• Model: Manages the data and business logic, similar to MVC.
• View: Responsible for displaying data and forwarding user interactions to the Presenter. Typically, it is an interface implemented by Activities, Fragments, or custom views.
• Presenter: Acts as a middleman between the View and Model. It retrieves data from the Model, processes it, and determines what the View should display. The Presenter communicates with the View via the View interface, ensuring better abstraction.

MVVM (Model-View-ViewModel)

MVVM introduces a more reactive approach by leveraging data binding and observables, which simplifies the communication between the View and ViewModel. It is a modern design pattern supported by Android Architecture Components.

• Model: Manages the application's data and business logic, similar to other patterns.
• View: Responsible for displaying data and binding to properties exposed by the ViewModel. In Android, this is typically an Activity or Fragment.
• ViewModel: Acts as an abstraction layer between the View and Model. It provides data and commands (actions) to the View through observable mechanisms like LiveData or RxJava. The ViewModel is lifecycle-aware, reducing the likelihood of memory leaks.
• Data Binding: Utilizes Android's Data Binding Library or other frameworks (e.g., LiveData, Flow) to automatically update the View when the data changes in the ViewModel. This reduces boilerplate code and improves readability.

MVI (Model-View-Intent)

MVI is a reactive design pattern that simplifies state management by treating the application's state as a single source of truth. It emphasizes immutability and unidirectional data flow.

• Model: Represents the state of the application and business logic.
• View: A stateless component that renders the UI based on the Model's state and sends user actions (Intents) to the Intent layer.
• Intent: Processes user actions and updates the Model, often by interacting with a backend or other data sources.

Key Characteristics:

• Unidirectional data flow ensures consistency and predictability.
• The entire UI is represented as a single state object, making debugging easier.
• Commonly used with reactive libraries like RxJava or Kotlin Coroutines with StateFlow.

When to Use:

• Apps requiring complex state management.
• Projects benefiting from clear separation of concerns and immutability.
• Real-time applications like chat or live updates.

Clean Architecture

Clean Architecture focuses on organizing code into layers to achieve high testability, maintainability, and separation of concerns. The dependency rule states that inner layers should not depend on outer layers.

• Entities: Core business logic and rules.
• Use Cases/Interactors: Application-specific business logic.
• Interface Adapters: Converts data between use cases and the external world (e.g., Presenters, ViewModels).
• Frameworks & Drivers: External dependencies like databases, UI frameworks, and APIs.

Key Characteristics:

• Promotes testability by isolating business logic from external dependencies.
• Each layer is independent and focuses on a specific responsibility.
• Decoupling allows for easier modifications and scalability.

When to Use:

• Large, scalable applications with long-term maintenance requirements.
• Projects with complex domain logic.
• Teams that prioritize unit testing and clean separation of concerns.

Comparing MVI and Clean Architecture