C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Help with helper classes          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Tim Woodburn Guest Posted: Thu Oct 21, 2004 7:41 pm    Post subject: Help with helper classes I have been looking for an example of helper classes. The problem I have is that I want to send messages between different classes. My MFC application has a tree of objects on a splitter window, a flex grid in another and a map in another. I am dragging an icon from the tree over the map and logging the position where the left mouse button is released. I want to send the map that position so it can display the icon in the appropriate place. I also want to update the list in the flexgrid etc. When I click on an entry on the flexgrid, I want the map to highlight the target. <End platform specific detail> So my question is, how are helper classes defined? A colleague showed me some UML where the flexgrid, map and tree classes were aggregates of a GUI class. Each of the aggregates has a pointer to the GUI class which is stored when the class is instantiated by the constructor. He explained that I would call a method in the GUI class from one of the aggregates and the GUI method would route the messages to the appropriate aggregates. When I was shown this on paper, I understood the concept. Unfortunately I have not been able to translate this into code. Could someone show me a simple example (unrelated to the above!) of a helper class with aggregated classes or point me to a suitable tutorial? Or is there better way of doing this? Thank you Tim [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Michael Kurz Guest Posted: Sat Oct 23, 2004 2:25 pm    Post subject: Re: Help with helper classes "Tim Woodburn" <tim (AT) robotcrazy (DOT) com> schrieb im Newsbeitrag news:56aa5822.0410210338.5712811f (AT) posting (DOT) google.com... Quote: I have been looking for an example of helper classes. The problem I have is that I want to send messages between different classes. My MFC application has a tree of objects on a splitter window, a flex grid in another and a map in another. I am dragging an icon from the tree over the map and logging the position where the left mouse button is released. I want to send the map that position so it can display the icon in the appropriate place. I also want to update the list in the flexgrid etc. When I click on an entry on the flexgrid, I want the map to highlight the target. End platform specific detail So my question is, how are helper classes defined? I would look at the observer pattern. Suggestion: -Introduce a kind of DragNDrop Manager (typically a Singleton) In the term of the observer pattern this Manager should be implement a kind of "Observable" Interface, which allows others (kind of clients) to register a callback for specific events: e.g something like: onIconDroppedNotification So if an Icon is dropped, the DragNDrop manager will notify all observers (which are registered). In general the observer pattern is often very usefuly (specially within GUI applications) to reduce dependencies. Regards Michael [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jeff Flinn Guest Posted: Sun Oct 24, 2004 4:10 am    Post subject: Re: Help with helper classes "Tim Woodburn" <tim (AT) robotcrazy (DOT) com> wrote Quote: I have been looking for an example of helper classes. The problem I have is that I want to send messages between different classes. My MFC application has a tree of objects on a splitter window, a flex grid in another and a map in another. I am dragging an icon from the tree over the map and logging the position where the left mouse button is released. I want to send the map that position so it can display the icon in the appropriate place. I also want to update the list in the flexgrid etc. When I click on an entry on the flexgrid, I want the map to highlight the target. End platform specific detail So my question is, how are helper classes defined? A colleague showed me some UML where the flexgrid, map and tree classes were aggregates of a GUI class. Each of the aggregates has a pointer to the GUI class which is stored when the class is instantiated by the constructor. He explained that I would call a method in the GUI class from one of the aggregates and the GUI method would route the messages to the appropriate aggregates. When I was shown this on paper, I understood the concept. Unfortunately I have not been able to translate this into code. Could someone show me a simple example (unrelated to the above!) of a helper class with aggregated classes or point me to a suitable tutorial? Or is there better way of doing this? See the boost signal library at: http://www.boost.org/doc/html/signals.html Jeff F [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Tim Woodburn Guest Posted: Wed Oct 27, 2004 12:59 am    Post subject: Re: Help with helper classes Thanks to Jeff and Michael for their replies. For the benefit of google I have found the following: An example of a simple implementation of the observer pattern from the code project "Implementing a Subject/Observer pattern with templates " http://bonxedes.notlong.com An article which was exactly what I was looking for from Code Project "Adding Behavior to Classes, Part I - An Introduction" http://kaiwogne.notlong.com [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Balog Pal Guest Posted: Wed Oct 27, 2004 1:00 am    Post subject: Re: Help with helper classes "Tim Woodburn" <tim (AT) robotcrazy (DOT) com> wrote Quote: The problem I have is that I want to send messages between different classes. To that you just need to find the class, then call the method. Or yo can use a mediator -- on windows the system is already in place, post a message, then it gets dispatched... Quote: My MFC application has a tree of objects on a splitter window, a flex grid in another and a map in another. I am dragging an icon from the tree over the map and logging the position where the left mouse button is released. I want to send the map that position so it can display the icon in the appropriate place. I also want to update the list in the flexgrid etc. When I click on an entry on the flexgrid, I want the map to highlight the target. End platform specific detail So my question is, how are helper classes defined? A colleague showed me some UML where the flexgrid, map and tree classes were aggregates of a GUI class. Each of the aggregates has a pointer to the GUI class which is stored when the class is instantiated by the constructor. If you use MFC why not do it the MFC way. It supports the document-view model, and what you describe fits it IMHO. Your document can have all the data, and you have 3 view to represent it, tree, map and grid. In that case it's not important whether they all live undes a single frame with splitters or some in distinct windows, or even if you have multiple of some views. On any view you handle the user event -- like D&D. You know what is dropped from the oledatasource, and figure out on what is it dropped. Then call the document with the event. (all views have a direct link to the document). The document rearranges the binary data, and sends update notification to all views broadcasting what actually changed (calling UpdateAllViews(pOriginatingView, longHint, pObjHint)). There's a good tutorial on MFC and doc/view architecture in MSDN, look up the SCRIBBLE sample, and follow the steps. Another approach could be to use the frame as the dispatch center. As your panes are child windows and all can post messages to GetParentFrame(). Like initially registering themselves for some events, then post their events. And the frame could then dispatch the messages to the interested parties. Quote: He explained that I would call a method in the GUI class from one of the aggregates and the GUI method would route the messages to the appropriate aggregates. That also caould be done, then foregt the MFC and do everything by hand. I currently see no benefit on working out another set of wheels. Paul [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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