MVC Architecture Pattern

MVC (Model-View-Controller) is an architectural pattern that divides an application into three interconnected components to separate internal representations of information from the ways information is presented and accepted by the user. It is the most widely used architectural pattern in web development.

1. The Three Components

Model

The Data Layer. Contains the business logic, data structures, and rules. It directly manages the data, logic, and rules of the application. The Model is completely independent of the user interface.

• Example: A User class with fields (name, email, password), validation rules, and database operations (save, find, delete).

View

The Presentation Layer. Displays data from the Model to the user. It is a visual representation of the Model. Multiple Views can exist for the same Model (a web page, a mobile app, and an API all showing the same data).

• Example: An HTML page that renders a list of users in a table.

Controller

The Logic Layer. Acts as the intermediary between the Model and the View. It receives user input from the View, processes it (possibly updating the Model), and determines which View to display next.

• Example: When a user submits a registration form, the Controller validates the input, tells the Model to create a new user, and redirects to a success View.

2. Flow of Control

1. The User interacts with the View (clicks a button, submits a form).
2. The View sends the user's action to the Controller.
3. The Controller processes the action, interacts with the Model (fetches or updates data).
4. The Model updates its state and notifies the View (or the Controller passes updated data to the View).
5. The View re-renders with the new data.

3. Variants

• MVP (Model-View-Presenter): The Presenter replaces the Controller. The View is more passive; all presentation logic lives in the Presenter. Used in Android development.
• MVVM (Model-View-ViewModel): Uses data binding so the View automatically updates when the ViewModel changes. Used in Angular, WPF, and SwiftUI.

4. MVC in Web Frameworks