Microsoft introduced an events system in VC++ 7 using keywords (event_source, event_receiver, __event, __raise, __hook, __unhook), expanding the language with a great tool.
This cool feature is not provided in VC++ 6.0 language.
My code provides users of VC++ 6.0 (could be used in other C++ systems) a simple events system, made in VC++ 6.0 and STL, with a small amount of code needed in order to use it.
The first thing to do is define the events provider, the events list and a struct that contains the events arguments.
The code is something like this:
1. Defining the events argument's list struct (inherited from EventArgs).
//**** Source Event Arguments
struct SourceEventArgs : EventArgs {
// Only have a int argument, but the
// structure could be more complex
int nRetCode;
// ... Others arguments needed for any Source class event
};
2. Declaring a class capable of "firing" the events (inherited from SourceEvents).
// Generate events
class Source : public SourceEvents {
...
};
3. Construct the "events" map
// Generate events
class Source : public SourceEvents {
protected:
//Events provided for this class
_BEGIN_EVENTS_HANDLER
_EVENT_HANDLER( Close )
_EVENT_HANDLER( Idle )
_END_EVENTS_HANDLER
...
4. Define methods to "fire" the events
// Generate events
class Source : public SourceEvents {
protected:
//Events provided for this class
_BEGIN_EVENTS_HANDLER
_EVENT_HANDLER( Close )
_EVENT_HANDLER( Idle )
_END_EVENTS_HANDLER
// Any name is acceptable but the standar is OnEventName
void OnIdle();
// this is a normal method that is calling for your code
// so any signature is correct ( Ex. int OnClose(int) ).
int OnClose(int);
...
//Implementation file
void Source::OnIdle() {
//_raise
SourceEventArgs e;
e.nRetCode = 0;
_raise(Idle, &e); // <-- this is the event launch
}
int Source::OnClose(int nRetCode) {
//_raise
SourceEventArgs e;
e.nRetCode = nRetCode;
_raise(Idle, &e); // <-- this is the event launch
return e.nRetCode;
}
Ok, now the we have the class Source, it can launch Close and Idle events for any number of event listener.
And now we need a class capable of listening to the events generated.
The code is simple
// Events Listener
class Target {
int m_code;
public:
Target(int i) : m_code(i) { }
//A normal way for declare this function is under protected and
//call this internally when the event have to be generated.
//Use the source object is not necesary but can help you
//for do some task.
void OnIdle(Source* pObj, SourceEventArgs* e) {
cout << "Target" << m_code <<
" el valor actual de e = " << e->nRetCode++;
cout << " " << pObj->Name() << endl;
}
// Return event value is allowed by use of structure
void OnClose(Source* /*pObj*/, SourceEventArgs* e) {
cout << "Target" << m_code <<
" el valor actual de e = "<< e->nRetCode << endl;
e->nRetCode = 4;
}
// Subscription function (Source is the class name for events
//generator class).
_DECLARE_HOOK_LIST( Source ) // <-- this is the declaration of listener.
};
// implementation file
// this define the hooks for each events catch for this class
// Source class name of events generator
// Target class name of events listener
// SourceEventArgs struct name of events arguments struct
_BEGIN_HOOK_LIST(Source, Target, SourceEventArgs)
_HOOK(Idle , OnIdle ) // Idle the name of event
_HOOK(Close, OnClose) // OnIdle the name of function how process the event
_END_HOOK_LIST
The last step is joining the object to listening events.
// Creating objects
Source s;
Target t(1);
// Joining listener for listening (t) events generated by Sourcer (s)
t.JoinTo(&s);
// launch events directly you may call this methods internally.
s.Idle();
s.Close();
//UnJoin
t.UnJoinTo(&s); // can use t.JoinTo(&s, false);
Remember that it is important to call the unjoin method before erasing the objects
Ok this it's my first one article and I expect that be of great aid. Please let me know and good look.
27 Nov 2002 - Initial Edit
3 Dec 2002 - updated downloads
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)
Thanks for reading.
, I have to search it, but thanks a lot for any help. 
, but I'm resubmit the code.