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--- xojo:objectnotifier:start [2021/04/01 17:20]
mz angelegt
+++ xojo:objectnotifier:start [2021/04/06 09:27] (aktuell)
mz [Object notification]
@@ Zeile 1: / Zeile 1: @@
-====== ObjectNotifier ======
+====== Object notification ======
-/* {{tag> }} */
-{{indexmenu>.#3|ns tsort hsort nsort}}
+<fs x-large>A simple subscribe-callback mechanism for inter-object communication</fs>
-----
+<WRAP round download 40%>
+**{{ :xojo:objectnotifier:object_notification.zip |Object Notification interfaces and class  (xojo-binary-code folder)}}**\\
+{{ :xojo:objectnotifier:objectnotification.pdf |Sourcecode as pdf}}
+</WRAP>
+This works similar to the built-in interfaces //dataNotifier// and //dataNotificationReceiver//.\\
+However the **ObjectChanged** method receives two parameters: an **Object** from the notifier and any **info** from the original subscriber.\\
+The **notifier** may send himself by setting "me" as Object, or he sends simply the current data which have been changed.\\
+The **subscriber** stores any sort of (static) information together with the callback-address when subscribing by //addObjectNotificationReceiver//.\\
+This info may be a simple index number, but it can also be a whole object (means a reference to an object) so that the receiver can distinguish which subscription called him.
+The **//ObjectNotifierBox//** contains the complete implementation of the //objectNotifier// interface.\\
+Simply instantiate this class and call their members like:
+Declare:
+  private property onb as ObjectNotifierBox
+in //Constructor// Method:
+  onb = new ObjectNotifierBox
+Actual implementation of the //objectNotifier// Interface:
+  Sub addObjectNotificationReceiver(receiver as objectNotificationReceiver, optional info as Variant = nil)
+     onb.addReceiver(receiver, info)
+  End Sub
+  Sub removeObjectNotificationReceiver(receiver As objectNotificationReceiver)
+     onb.removeReceiver(receiver)
+  End Sub
+For calling all subscribed receivers write somewhere in your class:
+  onb.callReceivers(me)
+Instead of "me" you may send any object you need, of course...
+<WRAP round important 100%>
+Be careful with //removing// if you have multiple subscriptions from the same object (perhaps with different //info//).\\
+<code>
+xy.addObjectNotificationReceiver(me, 1)
+xy.addObjectNotificationReceiver(me, 2)
+</code>
+Because //removeObjectNotificationReceiver// obtains no //info// parameter, it cancels only the first object found in the array, thus acting as //fifo//.\\
+It's therefore not possible to delete only the second entry (with //info// 2).
+</WRAP>
+====== Sourcecode ======
+{{ :xojo:objectnotifier:objectnotification-tree.png|}}
+===== Interface objectNotifier =====
+  Interface objectNotifier
+  Methods
+  Sub addObjectNotificationReceiver(receiver as objectNotificationReceiver, optional info as Variant = nil)
+  End Sub
+  Sub removeObjectNotificationReceiver(receiver As objectNotificationReceiver)
+  End Sub
+  End Interface
+===== Interface objectNotificationReceiver =====
+  Interface objectNotificationReceiver
+  Methods
+  Sub objectChanged(obj as Object, info as Variant)
+  End Sub
+  End Interface
+===== Class ObjectNotifierBox =====
+  Class ObjectNotifierBox
+  Methods
+  Sub addReceiver(receiver as objectNotificationReceiver, info as Variant)
+     var i as Integer = mReceivers.IndexOf(receiver)
+     if i = -1 then
+        mReceivers.Add(receiver)
+        mInfos.Add(info)
+     end if
+  End Sub
+  Sub callReceivers(obj as Object)
+     For i As Integer = 0 To mReceivers.LastIndex
+        mReceivers(i).objectChanged(obj, mInfos(i))
+     Next
+  End Sub
+  Sub removeReceiver(receiver As objectNotificationReceiver)
+     var i as Integer = mReceivers.IndexOf(receiver)
+     if i > -1 then
+        mReceivers.RemoveAt(i)
+        mInfos.RemoveAt(i)
+     end if
+  End Sub
+  Properties
+  Private mInfos() As Variant
+  Private mReceivers() As objectNotificationReceiver
+  End Class
 ----
 /*eof*/