Function pointer problem as an event

[EngineersForge]

First of all, thank u all for the help so far! It is very quick and right on the money.

Now, I wish to use a function pointer as an event raised by a class type inherited by another. This is in a basic console, single thread for now as I am just testing the class hierarchy.

I have one public

void (*fpRaiseEvent) (void);

function pointer that is called also in a public fucntion. The main program defines the function to just print out some text. When I invoke the method from an instance of the class everything is ok. Now when I copy the class by another class object things go south some where in the copy constructor. This is my code:

sinc. func. pointers:
*fpReqSer = *rhs.fpReqSer; //complies but does not work
assign func. pointer:
void (*fpReqSer) (void) = rhs.fpReqSer; // complies but does not work
also complies:
fpReqSer = rhs.fpReqSer; //does not work

Their are many other combinations haha, all of which cause an access violation at run time. The more I stare at the pointer arithmetic, the less I know??? How does one assign the ‘being copied object’s’ pointer already assigned, to also let the coping object point to the same function?

Tanx

 

[Cagliostro]

I'm not sure I understood well you, but there is a short sample of using pointers to global functions and to class members functions:
void xxx()
{
cout<< &quot;xxx&quot;<< endl;
}
class aaa
{
int x;
public:
aaa(int _x): x(_x){}
void xxx()
{
cout<< &quot;aaa:xxx>&quot;<< x << endl;
}
};
class bbb: public aaa
{
};

int main()
{
void (*ss)();
ss = xxx;
ss();
void (aaa::*sa)();
sa = &aaa::xxx;
aaa a(123);
(a.*sa)();
return 0;
}


Ion Filipski

ICQ: 95034075
AIM: IonFilipski
filipski@excite.com

 

[Cagliostro]

this one is with inheritance:
class aaa
{
int x;
public:
aaa(){}
aaa(int _x): x(_x){}
virtual void xxx()
{
cout<< &quot;aaa:xxx>&quot;<< x << endl;
}
};
class bbb: public aaa
{
int x;
public:
bbb(int _x): x(_x << 2){}
void xxx()
{
cout<< &quot;aaa:xxx>&quot;<< x << endl;
}
};

int main()
{
void (aaa::*sa)();
sa = aaa::xxx;
aaa a(123);
(a.*sa)();
bbb b(123);
(b.*sa)();

return 0;
}


Ion Filipski

ICQ: 95034075
AIM: IonFilipski
filipski@excite.com

 

[PerFnurt]

The C++/OO way of using function ptrs is the virtual methods.

Would you perhaps consider passing a raise event interface ptr about instead of a function ptr?

class RaiseEventI
{
  public:
   virtual void Raise() = 0;
   ...
};

class RaiseSomeSpecificEvent : public RaiseEventI
{
  // Implement the Raise method
  ...
}

class Foo
{
  RaiseEventI* mRaiseEvent;
public:
  void Bar()
  {
     mRaiseEvent->Raise();
  }
}

etc


/Per

_{if (typos) cout << &quot;My fingers are faster than my brain. Sorry for the typos.&quot;;}

 

[EngineersForge]

Ok thank you for the samples; however, I am after something else. I don't wish to use an event object until later. As for the code by IonFilipski, I have to be honest, I have no idea. To cryptic.

Here is another attempt:

calss a
{
public:
void (*fpReqSer) (void);
void RequestService(void);
};

void a::RequestService(void)
{
//raise event
fpReqSer();
}

NOW

class b: public a
{
whatever...
};

NOW

void service1(void){print some stuff out};

void main(void)
{
b Foo;
Foo.fpReqSer = &Service1;

pod.RequestService();//works just fine

b Foo1(Foo);
Foo1.RequestService();//access violation ???
}

I think the problem must be int he copy constructor impl.

HERE IT IS

a::a(const a &rhs)
{
*fpReqSer = *rhs.fpReqSer; //something not right???
}

Could it be a question of security using Visuals C++ non ANSI/ISO compilier??? I don't see why one can't copy a pointer to a function from another class type of the same kind.

tanx

 

[adevadeh]

EF,

a::a(const a &rhs)
{
  //*fpReqSer = *rhs.fpReqSer; //something not right??? yes
  // try this
  fpReqSer = rhs.fpReqSer;  
}

I had this wonderful huge explanation written out, but I lost it when I clicked on preview. If you want to know why, just post again...

-adeh