Command pattern problem

[alexcpn]

Hi I have a Command class of type

class Command
{
T* m_objptr;
void (T::*method)();

:

explicit Command(T* pObj,void (T::*p_method)( ),long timeout,const
char* key,long priority = PRIO_NORMAL ):
m_objptr(0),met hod(0),m_timeou t(timeout),m_ke y(key),m_value( priority)
{
m_objptr=pObj;
method = p_method;
}

inline void execute()
{
(m_objptr->*method)();
}
//-----------------------------------------------------------------------

I use this as

cmd= new Command<CTask>( task1,&CTask::D oSomeTask,task1-

>GetTimeOut()," ne2_11"PRIO_NOR MAL);

where CTask is defined as

class CTask
{
void DoSomeTask()

Question 1
Is this usage safe? ie will &CTask::DoSomeT ask point to the method
of CTask ?

I use this in a threadpool and I am sometimes getting thiings to work
and sometimes access violation (VC6 compiler)

Question 2
Is it possible that I can pass a parameter to the method

something like

class Command
{
T* m_objptr;
void (T::*method)(vo id *);


class CTask
{
void DoSomeTask(void *) or
static void DoSomeTask(void *)

If so how do you initiate Command class - I was getting compiler error
while doing this

cmd= new Command<CTask>( task1,&CTask::D oSomeTask(this) ,task1-

>GetTimeOut()," ne2_11"PRIO_NOR MAL);

Thanks for your time
Alex.C.P

[Michael DOUBEZ]

Re: Command pattern problem

alexcpn a écrit :

Hi I have a Command class of type
>
class Command
{
T* m_objptr;
void (T::*method)();
>
:
>
explicit Command(T* pObj,void (T::*p_method)( ),long timeout,const
char* key,long priority = PRIO_NORMAL ):
m_objptr(0),met hod(0),m_timeou t(timeout),m_ke y(key),m_value( priority)
{
m_objptr=pObj;
method = p_method;
}
>
inline void execute()
{
(m_objptr->*method)();
}
//-----------------------------------------------------------------------
>
I use this as
>
cmd= new Command<CTask>( task1,&CTask::D oSomeTask,task1-

>GetTimeOut()," ne2_11"PRIO_NOR MAL);

>
where CTask is defined as
>
class CTask
{
void DoSomeTask()
>
Question 1
Is this usage safe?

It is not safe but it is legal.

Your execute methode could be safer:
inline void execute()
{
if( (m_objptr!=NULL ) && (method!=NULL)
{
(m_objptr->*method)();
}
//else do nothing, throw an exception ...
}

ie will &CTask::DoSomeT ask point to the method
of CTask ?

Yes.

I use this in a threadpool and I am sometimes getting thiings to work
and sometimes access violation (VC6 compiler)
>
Question 2
Is it possible that I can pass a parameter to the method
>
something like
>
class Command
{
T* m_objptr;
void (T::*method)(vo id *);
>
>
class CTask
{
void DoSomeTask(void *) or
static void DoSomeTask(void *)
>
If so how do you initiate Command class - I was getting compiler error
while doing this
>
cmd= new Command<CTask>( task1,&CTask::D oSomeTask(this) ,task1-

>GetTimeOut()," ne2_11"PRIO_NOR MAL);

The types are not the sames: &CTask::DoSomeT ask is a void
(CTask::*)(void *) when a void (CTask::*)(void *) is expected.

You could use mem_fun structures for standard application but the
easiest is to use boost::function type boost::function 0<void>.

Michael