Passing Class Pointers...

Whoa, cowboy. this is NOT a type, so I don''t know what it''s doing in your parameter lists and return values. this is the pointer to the object being called, and its type is the object type (MessageRegistry in this case).

I think what you need to have as a type is the base class for your messages, like so:

class MessageRegistry { public: RegisterMessageID (unsigned char messageid, MessageHandlerPtr* sender) { Registry.insert(messageid, sender); } // etc., etc. };

Also, very important, I think you''ve mis-defined MessageHandlerPtr as a MessageRegistry*. It should be a MessageHandler*, and you should have MessageHandler be some pure-virtual base class with the actual message-handling function to be overloaded by derived message-handler objects.

If I were using this class, I would make one object of the MessageRegistry class exist in the main class object--don''t make it a heap variable (i.e. don''t "new" it), because you only want one instance and you want it to go away when the program ends. Since the class doesn''t dynamically allocate memory, you don''t need a destructor to free anything. Actually, you could even derive your main class from MessageRegistry and have it do what you want.

I think what the author intended was for each of your message handler objects to have one instance of themselves somewhere, and for the constructor for each object to register itself with the MessageRegistry. For instance:

// WidgetHandler.h
class WidgetHandler : public MessageHandler
{
  WidgetHandler ()
  {
    mainClassPtr->RegisterMessageID (WIDGET_CODE, this);
  }
};
 

Now the real question comes as to where the object of WidgetHandler will be declared. This is tricky, because you must be certain that mainClassPtr has finished being constructed before any of the handlers are constructed. I''m not sure of the answer, but I could read the article & probably figure it out. Hope this has helped get you on the right path.

Ahhh... ok. I''ve had a bit of a rethink of my implementation. I''ve reread my manual on static member functions and class pointers and think I''m a bit closer. The ''this'' part should now be ok too (I think) as even derived objects hsould still have the same base type(I think thats how inheritence works)

Here is a new copy:

typedef vector<unsigned char> ByteArray; enum MESSAGEID { TEXT_MESSAGE, MESSAGE_QUIT, MESSAGE_MOVEMENT1 }; /////////////////////////////////////// class BaseMessageIndex { public: protected: void RegisterID(MESSAGEID messageid) { IDRegistry.insert((unsigned char)messageid,this); } void RegisterString(string &messagestring) { StringRegistry.insert(messagestring,this); } typedef map<unsigned char, BaseMessageIndex*> IDRegistryMap; typedef map<string, BaseMessageIndex*> StringRegistryMap; static IDRegistryMap IDRegistry; static StringRegistryMap StringRegistry; }; class MessageSwitch : public BaseMessageIndex { public: void MessageData(ByteArray &Data) { if (Data[0] == TEXT_MESSAGE) { //Data is string based. Check string map.(case insensitive) } else { //Data is ID based. Check ID map. } } }; class QuitMessageHandler : public BaseMessageIndex { public: QuitMessageHandler() { RegisterID(MESSAGE_QUIT); RegisterString(NULL + "QUIT"); } private : static void dummy(void); };

I''m still having problems with the inserts. Specifically with this error:

c:\program files\microsoft visual studio\vc98\myprojects\pluggablefactory\plug.h(26) : error C2664: ''class std::_Tree


std::char_traits,class std::allocator > >,class std::allocator >::iterator''
No constructor could take the source type, or constructor overload resolution was ambiguous

I hope your able to help, I feel so close now...

Once again, many thanks.

Chris ''gimp'' Brodie