Changes between Version 1 and Version 2 of ObserverHowto

Timestamp:

Sep 13, 2012, 1:58:53 PM (12 years ago)

Author:

ankele

Comment:

Observable's constructor missed channel creation

ObserverHowto

@@ -3 +3 @@
 == Theory ==
 
-The ''Observer'' pattern is a way of implementing a one-to-many dependency. There usually is one observable object automatically notifying multiple observer objects of its changes. For doing so the observer keeps a list of its observables. The observables in turn have to sign on to the observer's list.
+The ''Observer'' pattern is a way of implementing a one-to-many dependency. There usually is one observable object automatically notifying multiple observer objects of its changes. For doing so the observer keeps a list of its observables. The observers in turn have to sign on to the observable's list.
 
 == Implementation ==
@@ -11 +11 @@
   * derive the observable class from {{{Observable}}}
   * create an enum type with one element for each type of change about to occur
+  * in the constructor call the {{{Observable}}} constructor giving a string name for your class
+  * also in the constructor create the channels (see code below)
   * surround any code that makes notify-worthy changes with {{{OBSERVE;}}} and {{{NOTIFY(channel);}}} with {{{channel}}} the appropriate enum constant
 
@@ -18 +20 @@
   class MyObservable : public Observable
   {
-    ...
   public:
     enum NotificationType{ // should be public (the observer will want to use this type!)
       SomethingDone,
-      OtherStuffDone
+      OtherStuffDone,
+      NotificationType_MAX
     };
+    MyObservable() : Observable("MyObservable")
+    {
+      Channels *OurChannel = new Channels;
+      NotificationChannels.insert( std::make_pair(this, OurChannel) );
+      // add instance for each notification type
+      for (size_t type = 0; type < NotificationType_MAX; ++type)
+        OurChannel->addChannel(type);
+      // other constructor stuff
+      ...
+    }
+    ....
     void doSomeChanges()
     {