you could also try somthing like the following.

create a concept of an information package in your game. information packages would all be derived from some base class, and they would all be stored in a central place (perhaps a global singelton named something like InformationPackageManager). Each time a unit wants to share information with other units it would create an information package and somehow broadcast a notice to (either all nearby units, or a specific unit, or whatever) the notice contains just the package ID with which the information can be retrieved from the InformationPackageManager. you can add expiration dates on the information so you don't end up with information package overload at the end of the game. if a unit tries to retrieve an invalidated package the function just returns and error and the unit just continues as if that information wasn't present. you can build in intelligence to the information expiration such that if only one unit knows this info, and it dies, then the info gets expired instantly.

For the Info packages themselves, perhaps have a single enumerated type or something similar loaded from a text file where you define each number to mean a specific thing like: "enemy close to my position", "need backup", "man down", whatever. perhaps the info packet would need one other field like an int or a pointer or whatever.

thus, you could do something like:

union AnyType {    int *ival;    float *fval;    double *dval;    char *sval;};class InfoPackage {    MessageType msgType;    AnyType data;};

at any given moment in your AI update loop, units can call something like:

InfoID newInfoID = InformationPackageManager->addInformation(msgType, data);UnitsList receiveUnits = someFunctionToGetTargetUnits();for (int i = 0; i < receiveUnits.size(); ++i)    receiveUnits[i]->sendInfo(newInfoID); 

so basically you just send out alerts to specific units that there is new data they should look at and you just pass them an info id. if they choose to look at the data, are able to hear you, whatever, they can just look up the data from the infomation warehouse and alter their behavior based on that info. you end up with only one instance of each piece of information and a quick and low data traffic way to pass information around. the only trick is in getting rid of that data when it's no longer needed so you don't get memory bloat.

then again, i have no idea what your specific problem is, so let me know if that helps at all and perhaps i can add some more brainstorming...

-me

[edited by - Palidine on January 5, 2004 5:24:59 PM]

What I did was create a SuperClass to all my subclasses with a function called Event(int, DWORD, DWORD, void*). That int is an enum''ed event (enum EVENT_TYPE{EVENT_TOUCHED, EVENT_KILLED,...} the two DWORDs are the ID''s of the sender and receiver, and the void* is a void* to a parameter that can be used (for instance in EVENT_DAMAGED, it contains an int that is the amount of damage to deal). Of course, you have to know what the parameter''s going to be, so in your Event function you can cast it to the proper type. Then I have a global function (you could also encapsulate this) called SendEvent, that takes all of those parameters and then sends off the event to the sender/receiver.

I just used a message singleton and each class would have a copy of the same msg handler. The classes/objects would then register with the msg handler in their initialisation giving it a uniqie ID. The Msg handler then created a queue for each registered class to hold its messages.

It was up to the classes to check for mail in by calling the msngr handler, which just returned the message at the front of the queue.

In addition to the queue, each class could register a function/callback to be called by the msgr for really important messages, sort of like an interrupt. So normal priority messages would be placed in the queue to be checked at leasiure, while others such as QUIT etc. were initiated automatically.

Don''t know if it''s a good way to do it or not but it worked quite well for our game.