Question

我有以下ViewModel，我在构造函数中实例化CompositeCommand：

 public class ViewImportPreviewViewModel:BindableBase
    {
        private IEventAggregator eventAggregator;  //event aggregator to enable Studio button in different ViewModel

        private readonly IRegionManager regionManager; //region manager for navigation to the main menu

        public CompositeCommand finalizeImportClick;//composite command to register multiple command for finalize import button click


        public ViewImportPreviewViewModel(IRegionManager regionManager, IEventAggregator eventAggregator, CompositeCommand finalizeImportClick) //constructor
        {
            this.eventAggregator = eventAggregator;
            this.regionManager = regionManager;

            this.finalizeImportClick = finalizeImportClick;
            finalizeImportClick.RegisterCommand(new DelegateCommand<string>(NavigateToMain)); //register a delegate command for finalize import button click


        }


        //subscriber method to the firs delegate command registered with finalize button click
        private void NavigateToMain(string argument) 
        {
            //it enables the studio button after import and sends it to the main menu view XAML
            eventAggregator.GetEvent<ButtonEnableEvent>().Publish("ImportDone");

            //it navigates to the main menu after import
            regionManager.RequestNavigate("ScreenNavigationRegion", argument); 

            //publish an event for the main buttons viewmodel and then over there try to fade in main buttons
            eventAggregator.GetEvent<FadeinButtonsEvent>().Publish("ImportDone");
        }


    }

现在我想进行控制反转，并在类外部实例化CompositeCommand，然后通过Unity Container注入它，如下所示：

  CompositeCommand myCommand = new CompositeCommand();
  container.RegisterInstance<CompositeCommand>(myCommand);

然后在模块初始化时，我这样做：

NavigateToMain(string argument)

虽然命令已注册，但我没有收到任何错误，但RegisterCommand没有被调用。

我尝试注册类型，但CompositeCommand继承了ICommand接口，该接口不包含/[^\u0000-\u024F\u1E00-\u1EFF\u2C60-\u2C7F\uA720-\uA7FF]/g方法的定义。

Answer 1

实际上，CompositeCommands是单例/静态非常常见，因为多个松散耦合的模块将注册相同的CompositeCommand。这是标准的，也是预期的。

当然，您希望这样做以保持ViewModel的可测试性。您希望通过ctor知道您的依赖项。您不希望在VM中调用静态方法。

您要做的是创建一个自定义界面，如IApplicationCommands，并为您要公开的每个CompositeCommand提供属性，然后确保将该界面注册到您的容器。我还建议提供一个静态版本，以便您可以将按钮绑定到compositeCommands而无需引用绑定，这非常好。

所以也许是这样的：

    //Create an interface to abstract away the implementation of the static GlobalCommands class
public interface IGlobalCommands
{
    CompositeCommand SaveAllCommand { get; }
}

public static class GlobalCommands
{
    public static CompositeCommand SaveAllCommand = new CompositeCommand();
}

//Create a facade around the static GlobalCommands class
public class GloablCommandsFacade : IGlobalCommands
{
    public CompositeCommand SaveAllCommand
    {
        get { return GlobalCommands.SaveAllCommand; }
    }
}

并注册如下：

//register our global commands facade with the container as the IGlobalCommands interface so that we can ask for this service in our VM constructors
        // and remove the call to a static class in our VM.  This keeps us testable.
        Container.RegisterType<IGlobalCommands, GloablCommandsFacade>();

如何对CompositeCommand进行控制反转？

1 个答案: