Understanding ViewModel Instantiation with MediatR Publish and Splat in Avalonia Projects

In this article, we will be discussing how to use MediatR Publish and Splat for ViewModel instantiation in Avalonia projects. This is a great way to implement the Mediator pattern in your application, which can help to decouple the different components of your application and make it more maintainable.

But before we dive into the details, let's first discuss what MediatR Publish and Splat are and how they can be used to instantiate ViewModels in Avalonia projects.

What is MediatR Publish?

MediatR is a simple mediator library for .NET that allows you to send and receive messages between different parts of your application. It can be used to implement the Mediator pattern, which is a way to decouple the different components of your application by using a mediator object to handle the communication between them.

MediatR Publish is a feature of MediatR that allows you to send a message to all interested parties in your application. This can be useful for implementing event-driven architectures, where different components of your application can react to events that are triggered by other components.

What is Splat?

Splat is a simple dependency injection container for .NET. It is designed to be lightweight and easy to use, and it can be used to manage the dependencies of your application. It can be used to register and resolve dependencies, and it can also be used to create scoped dependencies.

Using MediatR Publish and Splat for ViewModel Instantiation

In Avalonia projects, you can use MediatR Publish and Splat to instantiate ViewModels. This can be done by creating a ViewModelLocator class that uses Splat to register and resolve ViewModels, and that uses MediatR Publish to notify interested parties when a ViewModel is instantiated.

Here is an example of how this can be done:

using MediatR;
using Splat;
using System.Threading.Tasks;

public class ViewModelLocator
{
    private readonly IMediator _mediator;

    public ViewModelLocator(IMediator mediator)
    {
        _mediator = mediator;
    }

    public async Task ResolveViewModel() where TViewModel : class, IViewModel
    {
        var viewModel = Locator.Current.GetService();

        if (viewModel == null)
        {
            viewModel = Activator.CreateInstance();

            await _mediator.Publish(new ViewModelInstantiatedNotification());
        }

        return viewModel;
    }
}

public class ViewModelInstantiatedNotification : INotification
{
}

In this example, the ViewModelLocator class is responsible for resolving ViewModels. It uses Splat to register and resolve ViewModels, and it uses MediatR Publish to notify interested parties when a ViewModel is instantiated. The ViewModelInstantiatedNotification class is used to notify interested parties of the ViewModel instantiation.

To use this ViewModelLocator class, you can do the following:

public class MainWindowViewModel : IViewModel
{
    private readonly IMediator _mediator;

    public MainWindowViewModel(IMediator mediator)
    {
        _mediator = mediator;

        _mediator.Register(<ViewModelInstantiatedNotification>
            (notification) =>
            {
                // Do something when the MainWindowViewModel is instantiated
            });
    }

    // ...
}

In this example, the MainWindowViewModel class is registered to receive a notification when the MainWindowViewModel is instantiated. This can be used to perform some initialization logic when the ViewModel is created.

In this article, we have discussed how to use MediatR Publish and Splat for ViewModel instantiation in Avalonia projects. This is a great way to implement the Mediator pattern in your application, which can help to decouple the different components of your application and make it more maintainable. We hope that this article has been helpful and that you will be able to use MediatR Publish and Splat in your own Avalonia projects.

References

I hope you enjoyed this article and found it helpful. Please let me know if you have any questions or comments, and I'll be happy to help. Thank you for reading!