Software Engineering: Model View ViewModel (MVVM)

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Tiempo de lectura: 3 minutos

The term “Model-View-ViewModel” (MVVM) is a software architecture pattern commonly used in the development of software applications, especially in user interface applications such as web and mobile apps. MVVM is a variant of the Model-View-Controller (MVC) pattern and focuses on separating the presentation logic from the business logic of an application.

In MVVM, the three main components are:

  • Model: Similar to Model-View-Controller (MVC), the Model represents the data and business logic of the application. This can include operations such as retrieving data from a database, performing calculations, and applying business rules.

Example:

public class UserModel {
    private String username;
    private String email;
    
    // Constructor, getters, and setters
}

In this example, the UserModel represents user data, including the username and email address.

  • View: The View is the user interface presented to the end user. In MVVM, the view handles the presentation and visual structure of the application. The view does not contain business logic; it simply displays information and responds to user interactions.

Example:

<!-- XML layout file for the view (example for Android) -->
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/usernameTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView
        android:id="@+id/emailTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

In this example, the user_profile.xml view defines the user interface to display user details, such as the username and email address.

  • ViewModel: The ViewModel acts as an intermediary between the Model and the View. It is responsible for handling the presentation logic and view logic of the application. The ViewModel is specific to the view and contains the necessary logic to present data in the appropriate format for the view. It can also handle user events and actions from the view, such as button clicks or input field changes. Additionally, the ViewModel communicates with the Model to fetch and update data as needed.

Example:

public class UserViewModel {
    private UserModel userModel;
    
    public UserViewModel(UserModel userModel) {
        this.userModel = userModel;
    }
    
    public String getUsername() {
        return userModel.getUsername();
    }
    
    public String getEmail() {
        return userModel.getEmail();
    }
}

In this example, the UserViewModel acts as an intermediary between the UserModel and the view. It provides methods to get the user data in a way that is suitable for the view.

Differences between Model-View-ViewModel and Model-View-Controller

The main difference between MVVM and MVC lies in how the presentation logic is handled and organized. In MVVM, the presentation logic is encapsulated in the ViewModel, allowing for greater separation of concerns and better code modularity. This facilitates unit testing of the presentation logic and the reuse of UI components in different parts of the application.

Technologies using Model-View-ViewModel (MVVM)

The Model-View-ViewModel (MVVM) architecture pattern is used in a variety of software development technologies, especially in user interface application development, such as web, mobile, and desktop applications.

Web technologies:

  • AngularJS, Angular, React, Vue.js: These frontend development frameworks for JavaScript enable the implementation of MVVM patterns to create interactive and dynamic web applications.
  • ASP.NET MVC, ASP.NET Core: Microsoft’s web development frameworks that support the MVVM pattern to create scalable and high-performance web applications.

Mobile technologies:

  • Android (with Kotlin or Java): The MVVM pattern is widely used in Android mobile application development using frameworks such as Android Architecture Components or third-party libraries like RxJava.
  • iOS (with Swift or Objective-C): In iOS application development, MVVM is implemented using frameworks like SwiftUI or UIKit along with design patterns such as Observables or Reactive Programming.

Desktop technologies:

  • WPF (Windows Presentation Foundation): In Windows desktop application development, MVVM is widely used with WPF due to its excellent support for the MVVM pattern and data binding.
  • JavaFX: For desktop application development in Java, MVVM can be implemented using JavaFX along with libraries like JavaFX Bindings for data binding.

Cross-platform technologies:

  • Flutter: A cross-platform development framework that uses the MVVM pattern to create mobile and desktop applications using a single codebase.
  • React: A development framework driven by Facebook for web and mobile development. It can also employ the MVVM model, though MVC is more common.
  • Xamarin: A cross-platform development platform that allows the development of native mobile applications for iOS, Android, and Windows using the MVVM pattern and the C# programming language.
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