zooflow

Message/EventBus.vb

@@ -0,0 +1,63 @@
+Imports System.Reflection
+
+''' <summary>
+''' A Simple EventBus for .NET
+''' https://stackoverflow.com/questions/368265/a-simple-event-bus-for-net
+''' </summary>
+Public Class EventBus
+    Private Shared _Instance As EventBus
+    Private _Listeners As List(Of EventListenerWrapper) = New List(Of EventListenerWrapper)()
+
+    Public Shared ReadOnly Property Instance As EventBus
+        Get
+            If IsNothing(_Instance) Then
+                _Instance = New EventBus()
+            End If
+            Return _Instance
+        End Get
+    End Property
+
+    Public Sub Register(ByVal listener As Object)
+        If Not _Listeners.Any(Function(l) l.Listener.Equals(listener)) Then
+            _Listeners.Add(New EventListenerWrapper(listener))
+        End If
+    End Sub
+
+    Public Sub Unregister(ByVal listener As Object)
+        _Listeners.RemoveAll(Function(l) l.Listener = listener)
+    End Sub
+
+    Public Sub PostEvent(ByVal e As Object)
+        _Listeners.
+            Where(Function(l) l.EventType = e.[GetType]()).
+            ToList().
+            ForEach(Sub(l) l.PostEvent(e))
+    End Sub
+
+
+
+    Private Class EventListenerWrapper
+        Public Property Listener As Object
+        Public Property EventType As Type
+        Private _method As MethodBase
+
+        Public Sub New(ByVal listener As Object)
+            Me.Listener = listener
+            Dim oType As Type = listener.[GetType]()
+            _method = oType.GetMethod("OnEvent")
+            If _method Is Nothing Then
+                Throw New ArgumentException("Class " & oType.Name & " does not containt method OnEvent")
+            End If
+            Dim oParameters As ParameterInfo() = _method.GetParameters()
+
+            If oParameters.Length <> 1 Then
+                Throw New ArgumentException("Method OnEvent of class " & oType.Name & " have invalid number of parameters (should be one)")
+            End If
+            EventType = oParameters(0).ParameterType
+        End Sub
+
+        Public Sub PostEvent(ByVal e As Object)
+            _method.Invoke(Listener, {e})
+        End Sub
+    End Class
+End Class