Board index » cppbuilder » Complie problem with callback funtion in component

2006-01-06 08:49:17 AM
cppbuilder81
I'm trying to write my first component from scratch. It's to
encapsulate the MS multi media timer. At this point its written as a
class so that I can easily test it.
I expect that either at design time or run time that an the user will
provide an event function such as OnMMMTimer(TObject *Sender).
In my header file:
protected:
typedef void (__closure *OnMMMTimerEvent)(TObject *Sender);
OnMMMTimerEvent FOnMMMTimerEvent; // binds ontimer event function
void __fastcall writeMMMTimerEvent( OnMMMTimerEvent NewMMMTimerEvent )
OnMMMTimerEvent __fastcall readMMMTimerEvent(void) { return
FOnMMMTimerEvent; }
public:
__property OnMMMTimerEvent OnMMMTimer =
{read=readMMMTimerEvent, write=writeMMMTimerEvent,
default=NULL};
In my cpp file
void CALLBACK TimerEvent(UINT ID, UINT D1, DWORD Sender, DWORD D2, DWORD D3)
{ // called by the timer thread
TMMMTimer::FOnMMMTimerEvent((TObject *) Sender);
}
I get this compiler error which I don't understand:
[C++ Error] MMMTimer.cpp(53): E2231 Member TMMMTimer::FOnMMMTimerEvent
cannot be used without an object
Thanks
Nate
 

"Nate Lockwood" < XXXX@XXXXX.COM >wrote in message
typedef void __fastcall (__closure *OnMMMTimerEvent)(TObject *Sender);
Incidently, the signature of your event (with __fastcall added) exactly
matches the signature of the existing TNotifyEvent event type, so you should
use that instead:
TNotifyEvent FOnMMMTimerEvent;
You do not need those. The declaration for the event can access the member
directly:
__property TNotifyEvent OnMMMTimer = {read=FOnMMMTimerEvent,
write=FOnMMMTimerEvent};
able to assign a handler at design time.
real object instance in order to access the event. Since you appear to be
passing the component's 'this' pointer as a user-defined value to the timer,
then you can use that ponter to reach the event, ie:
void CALLBACK TMyComponent::TimerEvent(UINT ID, UINT D1, DWORD dwUser,
DWORD dw1, DWORD dw2)
{
TMyComponent *pThis = reinterpret_cast<TMyComponent*>(dwUser);
if( pThis->FOnMMMTimerEvent )
pThis->FOnMMMTimerEvent(pThis);
}
{
//...
... = timeSetEvent(..., &TimerEvent, reinterpret_cast<DWORD>(this),
...);
//...
}
Gambit
 

Remy Lebeau (TeamB) wrote:
and here is how I'm trying to do it (with the changes you suggested).
But I get a compiler error:
[C++ Error] MMMTimer.cpp(54): E2247 'TMMMTimer::FOnMMMTimerEvent' is not
accessible
TimerEvent is not declared. If I declare it:
private:
void CALLBACK TimerEvent(UINT ID, UINT D1, DWORD dwUser, DWORD D2,
DWORD D3);
//---------------------------------------------------------------------------
void __fastcall TMMMTimer::StartTimer(void)
{
DWORD dwUser = reinterpret_cast<DWORD>(this);
ID = timeSetEvent(ThisPeriod, FResolution, TimerEvent, dwUser, Mode);
}
//---------------------------------------------------------------------------
void CALLBACK TimerEvent(UINT ID, UINT D1, DWORD dwUser, DWORD D2, DWORD D3)
{
TMMMTimer *pThis = reinterpret_cast<TMMMTimer*>(dwUser);
if( pThis->FOnMMMTimerEvent ) // compiler error
pThis->FOnMMMTimerEvent(pThis); // compiler error
}
TimerEvent is not declared. If I declare it:
private:
void CALLBACK TimerEvent(UINT ID, UINT D1, DWORD dwUser, DWORD D2,
DWORD D3);
and
//---------------------------------------------------------------------------
void CALLBACK TMMMTimer::TimerEvent(UINT ID, UINT D1, DWORD dwUser,
DWORD D2, DWORD D3)
{
TMMMTimer *pThis = reinterpret_cast<TMMMTimer*>(dwUser);
if( pThis->FOnMMMTimerEvent ) // compiler error
pThis->FOnMMMTimerEvent(pThis); // compiler error
}
//---------------------------------------------------------------------------
void __fastcall TMMMTimer::StartTimer(void)
{
DWORD dwUser = reinterpret_cast<DWORD>(this); // error next line
ID = timeSetEvent(ThisPeriod, FResolution, TimerEvent, dwUser, Mode);
}
//---------------------------------------------------------------------------
Then I get complier errors:
[C++ Error] MMMTimer.cpp(68): E2034 Cannot convert 'void (__stdcall *
(_closure )(unsigned int,unsigned int,unsigned long,unsigned
long,unsigned long))(unsigned int,unsigned int,unsigned long,unsigned
long,unsigned long)' to 'void (__stdcall *)(unsigned int,unsigned
int,unsigned long,unsigned long,unsigned long)'
and
[C++ Error] MMMTimer.cpp(68): E2342 Type mismatch in parameter 'fptc'
(wanted 'void (__stdcall *)(unsigned int,unsigned int,unsigned
long,unsigned long,unsigned long)', got 'void')
Nate
 

{smallsort}

"Nate Lockwood" < XXXX@XXXXX.COM >wrote in message
the component class.
'static':
private:
static void CALLBACK TimerEvent(UINT uID, UINT uMsg, DWORD dwUser,
DWORD dw1, DWORD dw2);
void CALLBACK TMMMTimer::TimerEvent(UINT uID, UINT uMsg, DWORD dwUser,
DWORD dw1, DWORD dw2)
{
TMMMTimer *pThis = reinterpret_cast<TMMMTimer*>(dwUser);
if( pThis->FOnMMMTimerEvent )
pThis->FOnMMMTimerEvent(pThis);
}
Gambit
 

Remy Lebeau (TeamB) wrote:
Nate
 

"Nate Lockwood" < XXXX@XXXXX.COM >wrote in message
handler is thread-safe.
Gambit