antigravity-skills-reference/skills/avalonia-viewmodels-zafiro/composition.md

Composition & Mapping

Ensuring your ViewModels are correctly instantiated and mapped to their corresponding Views is crucial for a maintainable application.

ViewModel-to-View Mapping

Zafiro uses the DataTypeViewLocator to automatically map ViewModels to Views based on their data type.

Integration in App.axaml

Register the DataTypeViewLocator in your application's data templates:

<Application.DataTemplates>
    <DataTypeViewLocator />
    <DataTemplateInclude Source="avares://Zafiro.Avalonia/DataTemplates.axaml" />
</Application.DataTemplates>

Registration

Mappings can be registered globally or locally. Common practice in Zafiro projects is to use naming conventions or explicit registrations made by source generators.

Composition Root

Use a central CompositionRoot to manage dependency injection and service registration.

public static class CompositionRoot
{
    public static IShellViewModel CreateMainViewModel(Control topLevelView)
    {
        var services = new ServiceCollection();
        
        services
            .AddViewModels()
            .AddUIServices(topLevelView);
            
        var serviceProvider = services.BuildServiceProvider();
        return serviceProvider.GetRequiredService<IShellViewModel>();
    }
}

Registering ViewModels

Register ViewModels with appropriate scopes (Transient, Scoped, or Singleton).

public static IServiceCollection AddViewModels(this IServiceCollection services)
{
    return services
        .AddTransient<IHomeSectionViewModel, HomeSectionSectionViewModel>()
        .AddSingleton<IShellViewModel, ShellViewModel>();
}

View Injection

Use the Connect helper (if available) or manual instantiation in OnFrameworkInitializationCompleted:

public override void OnFrameworkInitializationCompleted()
{
    this.Connect(
        () => new ShellView(),
        view => CompositionRoot.CreateMainViewModel(view),
        () => new MainWindow());

    base.OnFrameworkInitializationCompleted();
}

Tip

Use ActivatorUtilities.CreateInstance when you need to manually instantiate a class while still resolving its dependencies from the IServiceProvider.