在 Prism 6 中加载所有模块后使用 ViewModel 初始化 Shell

Question

我的 Shell / MainWindow 的 ViewModel（通过 AutoWireViewModel="True" 设置）请求一个依赖项，该依赖项在启动时使用 ConfigurationModuleCatalog 加载到模块中。
因为Shell在模块之前初始化，DI容器显然无法解析，所以应用崩溃了。

public class MainWindowViewModel : BindableBase
{
    // Cannot resolve IService
    public MainWindowViewModel(IService service)
    {
    }
}

我已经尝试了this post 的两种方法，但都没有奏效。

我是这样尝试的：

public interface IShellService
{
    int NumberOfLoadedModules { get; }

    void FlagModuleAsLoaded();
}

public class ShellService : IShellService
{
    private readonly IModuleCatalog _moduleCatalog;

    public ShellService(IModuleCatalog moduleCatalog)
    {
        _moduleCatalog = moduleCatalog;
    }

    public int NumberOfLoadedModules { get; private set; }

    public void FlagModuleAsLoaded()
    {
        NumberOfLoadedModules++;

        if (NumberOfLoadedModules != _moduleCatalog.Modules.Count())
            return;

        InitializeShell();
    }

    private static void InitializeShell()
    {
         Application.Current.MainWindow.Show();
    }
}

internal class Bootstrapper : UnityBootstrapper
{
    protected override DependencyObject CreateShell()
    {
        return null;
    }

    protected override void InitializeShell()
    {
    }

    protected override void ConfigureContainer()
    {
        base.ConfigureContainer();
        Container.RegisterInstance<IShellService>(new ShellService(ModuleCatalog), new ContainerControlledLifetimeManager());
    }

    protected override IModuleCatalog CreateModuleCatalog()
    {
        return new ConfigurationModuleCatalog();
    }
}

---

用法

public abstract class ModuleBase : IModule
{
    private readonly IShellService _shellService;

    protected ModuleBase(IShellService shellService)
    {
        _shellService = shellService;
    }

    public void Initialize()
    {
        InitializeInternal();
        FlagAsLoaded();
    }

    public abstract void InitializeInternal();

    public void FlagAsLoaded()
    {
        _shellService.FlagModuleAsLoaded();
    }
}

public class FooModule : ModuleBase
{
    IUnityContainer _container;

    public MusicUIModule(IUnityContainer container, IShellService shellService) : base(shellService)
    {
        _container = container;
    }

    public override void InitializeInternal()
    {
        _container.RegisterType<IService, Service>();
    }
}

它开始计算模块，然后应用程序由于同样的原因而崩溃。
如果上述方法不适合我的目的，该问题如何解决？

谢谢！

Answer 1

我尝试实施Haukinger's 建议并以这种方式进行，效果很好：

// Factory --------------------------------------------------------

public interface IDependencyFactory
{
    IService GetService();
}

public class DependencyFactory : IDependencyFactory
{
    private readonly IUnityContainer _container;

    public DependencyFactory(IUnityContainer container)
    {
        _container = container;
    }

    public IService GetService()
    {
        return _container.Resolve<IService>();
    }
}

// PubSubEvent ------------------------------------------------------

public class AllModulesLoaded : PubSubEvent
{
}

// Bootstrapper -----------------------------------------------------

internal class Bootstrapper : UnityBootstrapper
{
    protected override DependencyObject CreateShell()
    {
        return Container.Resolve<MainWindow>();
    }

    protected override void InitializeShell()
    {
        Application.Current.MainWindow.Show();
    }

    protected override void InitializeModules()
    {
        base.InitializeModules();

        // Publishing event to tell subscribers that the modules are loaded
        var eventAggregator = Container.Resolve<IEventAggregator>();
        eventAggregator?.GetEvent<AllModulesLoaded>().Publish();
    }

    protected override void ConfigureContainer()
    {
        base.ConfigureContainer();

        // ...
        Container.RegisterType<IDependencyFactory, DependencyFactory>();
    }

    protected override IModuleCatalog CreateModuleCatalog()
    {
        return new ConfigurationModuleCatalog();
    }
}

// ViewModel ---------------------------------------------------------

public class MainWindowViewModel : BindableBase
{
    private IService _service;
    private readonly IEventAggregator _eventAggregator;
    private readonly IDependencyFactory _dependencyFactory;

    public MainWindowViewModel(IEventAggregator eventAggregator, IDependencyFactory dependencyFactory)
    {
        _eventAggregator = eventAggregator;
        _dependencyFactory = dependencyFactory;

        _eventAggregator.GetEvent<AllModulesLoaded>().Subscribe(OnAllModulesLoaded);
    }

    private void OnAllModulesLoaded()
    {
        var service = _dependencyFactory.GetService();
        if (service != null)
            _service = service ;

        _eventAggregator.GetEvent<AllModulesLoaded>().Unsubscribe(OnAllModulesLoaded);
    }
}

Answer 2

我会将 shell 的依赖项隐藏在工厂/提供者后面，然后在加载最后一个模块时创建/获取它。当base.InitializeModules 返回时，您的shell 的视图模型订阅了一个AllModulesLoaded 事件，该事件从您的引导程序的InitializeModules 触发，以获取依赖项可用的通知。或者工厂/提供者订阅事件，shell 轮询它，这取决于您希望如何使用依赖项。