所示。當我開始想如何「下嫁」 MVVM和RX，我想到的第一件事是一個ObservableCommand：
public class ObservableCommand : ICommand, IObservable<object>
{
private readonly Subject<object> _subj = new Subject<object>();
public void Execute(object parameter)
{
_subj.OnNext(parameter);
}
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
public IDisposable Subscribe(IObserver<object> observer)
{
return _subj.Subscribe(observer);
}
}
但是後來我認爲綁定控件到ICommand屬性的「標準」MVVM方式並不是很RX'ish，它將事件流分解爲相當靜態的耦合。RX更多關於事件，並且聽取Executed路由事件似乎是適當的。以下是我想出了：
1）你必須要安裝在每個用戶控件的根應該響應命令一個CommandRelay行爲：
public class CommandRelay : Behavior<FrameworkElement>
{
private ICommandSink _commandSink;
protected override void OnAttached()
{
base.OnAttached();
CommandManager.AddExecutedHandler(AssociatedObject, DoExecute);
CommandManager.AddCanExecuteHandler(AssociatedObject, GetCanExecute);
AssociatedObject.DataContextChanged
+= AssociatedObject_DataContextChanged;
}
protected override void OnDetaching()
{
base.OnDetaching();
CommandManager.RemoveExecutedHandler(AssociatedObject, DoExecute);
CommandManager.RemoveCanExecuteHandler(AssociatedObject, GetCanExecute);
AssociatedObject.DataContextChanged
-= AssociatedObject_DataContextChanged;
}
private static void GetCanExecute(object sender,
CanExecuteRoutedEventArgs e)
{
e.CanExecute = true;
}
private void DoExecute(object sender, ExecutedRoutedEventArgs e)
{
if (_commandSink != null)
_commandSink.Execute(e);
}
void AssociatedObject_DataContextChanged(
object sender, DependencyPropertyChangedEventArgs e)
{
_commandSink = e.NewValue as ICommandSink;
}
}
public interface ICommandSink
{
void Execute(ExecutedRoutedEventArgs args);
}
2）視圖模型服務於用戶控制
public class ReactiveViewModel : INotifyPropertyChanged, ICommandSink
{
internal readonly Subject<ExecutedRoutedEventArgs> Commands;
public ReactiveViewModel()
{
Commands = new Subject<ExecutedRoutedEventArgs>();
}
...
public void Execute(ExecutedRoutedEventArgs args)
{
args.Handled = true; // to leave chance to handler
// to pass the event up
Commands.OnNext(args);
}
}
3）你不綁定控件ICommand的特性，但使用的RoutedCommand的代替：
public static class MyCommands
{
private static readonly RoutedUICommand _testCommand
= new RoutedUICommand();
public static RoutedUICommand TestCommand
{ get { return _testCommand; } }
}
0123從ReactiveViewModel繼承
而在XAML：
<Button x:Name="btn" Content="Test" Command="ViewModel:MyCommands.TestCommand"/>
其結果是，在你的視圖模型，你可以聽的很RX方式的命令：
public MyVM() : ReactiveViewModel
{
Commands
.Where(p => p.Command == MyCommands.TestCommand)
.Subscribe(DoTestCommand);
Commands
.Where(p => p.Command == MyCommands.ChangeCommand)
.Subscribe(DoChangeCommand);
Commands.Subscribe(a => Console.WriteLine("command logged"));
}
現在，你有路由命令的功率（您可以自由選擇處理層次結構中任何甚至多個ViewModel的命令），而且對於所有命令而言，對於RX來說都比單獨的IObservable更好。
平臺？ Silverlight的？ – AnthonyWJones 2009-11-19 13:54:34
安東尼：這很重要嗎？ – 2009-11-19 14:22:47