What is MVI architecture? How is it different than MVVM & MVP?

MVI stands for Model-View-Intent, which is an architectural pattern used primarily in Android app development. It aims to provide a clear separation of concerns, making the code more modular, testable, and maintainable. MVI focuses on unidirectional data flow, where the state of the application is managed in a single source of truth, typically using immutable data models.

Advantages of MVI Architecture

1. Unidirectional Data Flow: Simplifies the understanding of how data flows through the app, reducing the likelihood of bugs related to state management.
2. Single Source of Truth: The state of the application is centralized, making it easier to manage and debug.
3. Immutability: Encourages the use of immutable data models, which can lead to more predictable and easier-to-test code.
4. Testability: Each component is decoupled, making it easier to write unit tests for individual parts of the application.
5. Scalability: The clear separation of concerns allows the application to scale more easily.

Difference between MVI, MVVM, and MVP

• MVP (Model-View-Presenter): The View delegates user input to the Presenter, which acts as a middle-man, handling the logic and updating the View. The Model is responsible for the data and business logic.
  • Advantages: Clear separation between UI and business logic.
  • Disadvantages: Can lead to complex Presenter logic.
• MVVM (Model-View-ViewModel): The ViewModel exposes observable data and handles the UI logic. The View binds to this data and reacts to changes. The Model contains the business logic.
  • Advantages: Two-way data binding, decouples the UI from the business logic.
  • Disadvantages: Data binding can be complex and hard to debug.
• MVI (Model-View-Intent): The View emits user intents (actions), which are processed to produce a new state. The Model processes these intents and emits a new state, which is observed by the View.
  • Advantages: Unidirectional data flow, single source of truth, immutability.
  • Disadvantages: Can be verbose and have a steep learning curve.

MVI Architecture Diagram

+—————-+
| View |
+—————-+
|
| User Intents
v
+—————-+
| Intent |
+—————-+
|
v
+—————-+
| Model |
+—————-+
|
| State
v
+—————-+
| ViewState |
+—————-+
|
v
+—————-+
| View |
+—————-+

Explanation of Components

1. View: The user interface component that displays data and handles user interactions. It emits user intents (actions) based on user interactions.
2. Intent: Represents the user’s intention to perform some action. It is a clear representation of user actions or events.
3. Model: Handles the business logic and processes the intents to generate a new state. This state is immutable and represents the current state of the application.
4. ViewState: A representation of the state of the UI, which is produced by the Model and consumed by the View to render the UI.

Example Flow

1. User Interaction: A user performs an action on the View (e.g., clicks a button).
2. Intent: The View captures this action and translates it into an Intent.
3. Model: The Intent is sent to the Model, which processes it and generates a new ViewState.
4. ViewState: The new ViewState is emitted by the Model.
5. View Update: The View observes the new ViewState and updates the UI accordingly.

In summary, MVI architecture promotes a clear, predictable, and testable flow of data within an application, making it easier to manage complex state and business logic.