Separation of concerns in MVVM

The principle of separation of concerns is highly respected in software development. This concept makes it easier to fragment a complex problem into simpler, more manageable aspects. A key attribute of the MVVM architecture is its ability to facilitate this separation of tasks. This allows developers to focus on individual elements of the software separately, thus allowing them to more accurately understand and manage the complexity of the system.

Ease of maintenance and testing

The MVVM architecture pattern is hailed for its contribution to simplified application maintenance. The separation of program components makes it easier for developers to understand and manage the code. The clarity of the code structure created by MVVM, in turn, makes it easier to modify and add new features to the application. In addition, this architecture pattern increases the ease of testing, making it a better choice for developers.

Increased possibility of code reuse

Another important benefit of MVVM is its ability to promote code reuse. MVVM allows you to break down an application into smaller, manageable parts, which simplifies maintenance and allows you to create reusable templates. Developers can write view models and presenters in such a way that they can be effectively used in multiple applications with minimal changes. This reduces redundancy and increases productivity, as the same code can be reused for different functions or across projects.

Improved team collaboration

The MVVM architecture also plays a key role in improving team collaboration. Since the view models and presenters are written in code, they can be easily shared between developers. This code sharing eliminates potential confusion and misunderstandings that could arise if team members were working with different file types. As a result, MVVM improves communication and understanding within the development team, increasing overall project efficiency.

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When developing a SimpleOne application, we carefully design the user interface (UI) and design the user experience (UX) to make it easy and convenient for our customers to use the platform. But the UI is only the tip of the iceberg as seen by the user (User). Behind the buttons and fields lies code that must be scalable, maintainable, and reliable. To solve these problems, developers use MV* patterns to separate UI code, logic and data processing.

UI without patterns

Let’s imagine an application that has a form with various elements and widgets. The code of this form contains both the description of logic and the code of UI elements, and it may also contain fragments for data processing. For a simple application, supporting this programming principle is not a problem. At any moment you can find interrelationships and make changes without breaking the integrity. When the application becomes more complex, supporting an interface written without patterns becomes a problem.

The problem arises due to violation of the single responsibility principle – “A class should have only one reason to change”. We have UI code (View), logic (Controller), and data processing (Model) in our interface, so there are several reasons for change. When we change the code of one component, we have to change other components as well. Thus, application support becomes more complicated, it is almost impossible to perform automated testing, and code reuse is very limited.

That’s why it’s convenient and correct to use patterns – they separate UI code (View), logic code (Presenter, Controller, ViewModel and others) and data processing code (Model). We can easily change the logic without changing the UI, or make changes only to the data processing routines. Each pattern can be tested independently of the others and further used in other applications.

The most commonly used patterns are Model-View-Controller, Model-View-Presenter, and Model-View-ViewModel.

Patterns are not rigid paradigms that must be followed to create a perfect code organization. They solve very important problems – weakening (eliminating) the links between View, Model and Controller and reducing the complexity of user interface development. Realization of such approach is possible if you understand the essence of interconnections and look for the possibility of their elimination in each specific project.

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Benefits of using third-party libraries

• Save time: Ready-made solutions and components avoid writing a lot of code from scratch;
• Improved quality: Many libraries are thoroughly tested and optimized, which helps to avoid bugs and improve performance;
• Extensive features: Third-party libraries offer advanced features and capabilities that are difficult or time-consuming to implement on your own;
• Support and community: Popular libraries often have good documentation and an active community, making them easy to use and resolve issues that arise.

Popular third-party libraries for WPF

MVVM Light Toolkit is a lightweight and flexible framework for implementing the Model-View-View-ViewModel (MVVM) pattern. It simplifies code organization, improves testability, and contributes to more maintainable applications.

Prism is a powerful framework that helps you create modular and extensible WPF applications. It provides tools for dependency management, navigation and module deployment, which makes the development of complex applications more structured.

MahApps.Metro is a library that makes it easy to create modern and stylish Metro-style interfaces for WPF applications. It offers many ready-made components and styles that you can use to enhance the visual experience of your application.

MaterialDesignInXAML is a library for creating Material Design style applications. It provides a wide range of components and styles that will help you make your application’s interface modern and user-friendly.

AutoMapper is a library for automatic object mapping that helps you reduce the amount of code needed to convert data between different layers of your application.

How to integrate third-party libraries into a WPF project

Before integrating a third-party library, determine your needs and choose the right library that will help solve your problems. Read the documentation and use cases to understand how it works and what features it provides.

Most popular libraries are available through NuGet, a package manager for .NET.

After installing a library through NuGet, read the documentation to properly configure and use it in your project. The documentation usually provides code samples and explanations to help you quickly integrate the library and start using it.

After integrating the library, it is important to test your application to ensure that all components work correctly. Check that all dependencies are satisfied and that the application runs without errors. Use unit tests to verify the functionality provided by the third-party library.

Integrating third-party libraries into WPF projects is an effective way to speed up development, improve code quality and extend application functionality. Choosing the right tools and configuring them properly will help you create a more responsive, user-friendly and modern application that will satisfy users’ needs.

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• Default namespace: An XML function that defines a set of elements (and their attributes) that can be used in a document. At runtime, these elements are mapped to classes in the .NET assembly;
• Element: Using an XML element means that an object with the same name as the element will be created at runtime;
• Attribute: At runtime, the value of the attribute will be set to the value of the property of the object created for the corresponding element. The XAML parser can also convert text to non-text types, including a numeric type, an enumerated type, multiple initial values of a type (for example, different sides of a box), or an entire object initialized with attribute values (for example, a SolidColorBrush of a specific color);
• Nesting: placing one element inside another means that the created objects form a tree, whereby the nested object is assigned a default property (for example, one Child or Content property of the containing object) or it becomes one of several objects added to a default collection property (for example, a Children collection property);
• Property element: If an object property is too complex to declare or parse from a textual XML attribute, the property element syntax is used to fully declare the object;
• Attached properties: This allows the containing object to declare properties for each child object without requiring each child object’s class to have members (for example, a set of Button objects can be placed in a radial layout control that visually arranges buttons in a circle; this layout control requires each button to have an angle property value);
• Extensibility: To represent elements that become types from other .NET assemblies (such as other controls or classes), use this type of XML namespace declaration;
• x:Name: Similar to the ASP.NET ID attribute; to access created objects from within procedure code, give them a name;
• Evaluated: The {} syntax is used to evaluate a value at runtime, such as accessing resources or binding to data.

You can (and may need to in some cases) use the procedural code in the MainPage.xaml.cs file to create a user interface and populate it with data. However, XAML provides a more efficient way to declare visual interfaces instead of writing procedural code, which can be significantly longer. Procedural code is still used for data models and data access.

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Using data binding
Data binding is a key element in MVVM. It allows you to link interface elements to data and logic, ensuring that the interface is automatically updated when data changes. This makes it easy to create dynamic and responsive interfaces.

Command implementation
The use of commands in MVVM makes it easy to control user actions. Commands can be linked to interface elements such as buttons, providing a clear structure and organized code.

Feedback to the user
Feedback plays an important role in improving user interaction. Use notifications, loading indicators and animations to inform the user about the current state of the application and the operations being performed. This makes the application more interactive and understandable.

Asynchronous operations
To ensure smooth operation of the application, use asynchronous operations when performing long tasks to avoid user interface blocking and improve its responsiveness. Users don’t like to wait, so asynchronous operations and progress bars help create a sense of speed and efficiency.

Error and exception handling
Make sure your application handles errors and exceptions correctly. Show clear error messages to the user and provide instructions on how to fix them. This makes interacting with your app less stressful and more understandable.

Use animations and transitions
Animations and smooth transitions help make the interface more attractive and intuitive. In MVVM, it is easy to integrate animations that can be associated with ViewModel states. For example, animating the appearance of new data when a list is updated improves the user experience of the application.

Using MVVM to develop Windows Phone applications provides many opportunities to improve user interaction. This pattern helps to create a clear code structure, simplify data binding and event management, and improve the testability of the application. By following the above guidelines and utilizing the features of MVVM, you will be able to create a responsive and user-friendly application that will delight users.

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By extending the Behavior class, we can provide DependencyProperties along with regular properties that we can bind to properties from the ViewModel, so that when the properties of the ViewModel change, we can execute user interface code. The advantages of Behavior objects are that they can be easily reused, they are “blended” and allow us to move the code behind the View.

MVVM Light offers a Messenger class that is used by various objects to communicate in the application through a low-level communication mechanism. Messages can contain simple data types or more complex ones. This class is often used to allow ViewModel objects to communicate or to allow ViewModel objects to communicate with a View.

Another approach is to create interfaces that will be implemented by the View. For example, if we want to display notifications in a View, we can create an interface that exposes these methods, implement it in the View, and then add it to the ViewModel (we can get a reference to the ViewModel using the DataContext property).

It should be noted that the preferred way to handle this communication is with Behaviors, although MVVM does not explicitly state this, it is clear that as long as the code behind is minimized, the program is easier to test. The downside of Behaviors. is that they are not available in Windows 8 out of the box, so the code will be less portable, but there are libraries that offer classes similar to Behavior classes.

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Creating a model class

First, you need to create a Model class that will represent the data in your application. For example, if you’re developing a login feature, your model class could log the user’s email address and password. Keeping in mind the importance of a well-structured Model class, consider the following code to create a good Model class.

Working with the Activity_Main file

Next, you need to set up the Activity_Main file. This is the file where you will receive data from the user, such as email address and password. By adding EditText to the activity_main file, you can validate the user’s input and display the appropriate messages with the login button.

Creating the ViewModel class

Finally, it’s time to create the ViewModel class. This class will define the functionality of your application and manage the logic. It connects the model and the view, controlling the flow of data between them. To create an effective ViewModel class, you may want to consider using a structured approach similar to that of the Model class.

Defining view functions in the MainActivity file

In the MainActivity file, you can define the viewing functionality in the development of an Android application. This is the stage where the activity is introduced and the logic that implements the visual elements of the user interface design is implemented. The MainActivity file is essentially the center of the application, providing a place to manage the application lifecycle and process user interaction.

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MVP vs. MVVM

In the MVP architecture, the Presenter acts as a communication route between the model and the view. This solution reduces the dependence of the view on the model. However, in MVVM, the system is more event-driven, and the separation of the view from the underlying business logic is easier. In MVP, the user interface is used more often, while MVVM does not have a user interface model layer. In MVVM, observables are required because there is no view layer. The MVVM architecture sends the user data directly to the ViewModel, bypassing the presenter layer.

MVC vs. MVVM

Both MVC and MVVM are popular choices for software architecture in application development. MVC is a classic design pattern that is often chosen by many developers. However, MVVM offers a more modern approach, especially through the use of data binding to automatically update the user interface. In MVC, the controller is responsible for determining which view to display in response to any action, including user input. In contrast, MVVM uses a binder to automatically synchronize between the View and the ViewModel, thereby reducing the need for manual intervention.

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Using the DataBinding library

To implement MVVM using the DataBinding library, developers must first set up DataBinding in the project. This involves defining data classes or objects that represent the application data and creating XML layout files to define the user interface components. Next, you create ViewModel classes that process the logic and provide the data for viewing. Next, you implement DataBinding in the XML layout that connects the ViewModel and the view. Through the use of data variables, UI elements are linked to the ViewModel, establishing a connection between the UI and the underlying data.

Using RxJava for DataBinding

When it comes to implementing MVVM architecture, RxJava can be a powerful tool for data binding. By setting up DataBinding and RxJava in your project, you can effectively manage the flow of data and the interaction between user interface elements. This involves defining your data or object classes, creating your XML layout files, and handling the logic in your ViewModel classes.

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Data flow in MVVM

Data flow in MVVM is a key principle that keeps an application organized and maintainable. For example, pressing a button triggers an event in the View layer, which is then passed to the ViewModel. The ViewModel processes this event and updates the model accordingly. The model then handles the data persistence and business logic, resulting in a cyclical data flow that supports the user interface updates. This pattern effectively hides the business and validation logic from the View tier, ensuring a clear separation of concerns.

Model, View and ViewModel interaction

The interaction between Model, View, and ViewModel forms the basis of the MVVM architecture. Each of these components plays a separate role in the application. The Model handles data storage and business logic, serving as the server side of the application. ViewModel, acting as the model platform, handles user interactions and updates the model. On the other hand, the View provides the user interface by presenting data and accepting user input. This separation of roles in the architecture ensures efficient data flow and interaction within the computer software.

Delving into the code levels of MVVM

The MVVM architecture is divided into three key layers of code: the model, the view, and the view model. The Model tier is responsible for abstracting data sources, working together with the ViewModel to retrieve and store data. The View layer informs the ViewModel about user actions and observes changes in the ViewModel, but does not contain any program logic or user interface logic. The ViewModel layer opens data streams related to the View and serves as a link between the Model and the View. This multi-tiered structure facilitates the separation of tasks, improving the maintainability and scalability of the application.

Presentation tier

The presentation layer in the MVVM architecture is crucial for the user’s interaction with the application. This layer contains components such as activities, snippets, and view models. The role of the Activity is to facilitate communication between the user and the application, while the ViewModel is responsible for interacting with the domain layer to perform actions. It is important that the Activity should be as simple as possible, and all business logic should be encapsulated in the ViewModel. Such a division of tasks ensures the system’s modularity and efficiency, providing more focused development and easier debugging. In this process, creating a flawless user interface is extremely important.

Domain level

In the MVVM architecture, the domain layer is responsible for processing application use cases. It is here that actions are defined and executed, forming the main business logic of the system. This layer consists of abstract classes known as UseCases, which are extended by other classes to perform specific actions. The UseCaseHandler manages the execution of these use cases, ensuring that data retrieval actions do not block the user interface. The goal is to execute these actions in the background thread and deliver the response in the main thread, thus maintaining a seamless user experience.

Data layer

The data tier is an integral part of the MVVM architecture where all the repositories that interact with the domain tier are contained. This layer provides a data source API that the domain layer can use to retrieve or store data. The data tier decides whether to retrieve data from a local database or a remote server, thus providing flexibility and optimizing performance. The use of a binding adapter further simplifies the process of binding data between the data tier and the user interface, making the process more efficient and maintainable.

Advantages of MVVM architecture

The MVVM architecture, originally introduced by John Gossman, offers numerous advantages that have led to its widespread adoption by developers to create reliable and scalable applications. The architecture promotes code reuse, greatly simplifying the process of creating simple user interfaces. By separating the business logic from the user interface, MVVM facilitates independent testing of each layer, which ensures more reliable applications. The architecture also supports dependency injection, which provides better modularity and easier maintenance. With opportunities for increased code reuse and improved team collaboration, MVVM is the preferred choice for modern application development.

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