[punith]

hi i was going through Functor tutorial on net which had the following example

class TFunctor
   {
   public:
      virtual void operator()(const char* string)=0;
      virtual void Call(const char* string)=0;
 };

   template <class TClass> class TSpecificFunctor : public TFunctor
   {
   private:
      void (TClass::*fpt)(const char*);
      TClass* pt2Object;

   public:
      TSpecificFunctor(TClass* _pt2Object, void(TClass::*_fpt)(const char*))
         { pt2Object = _pt2Object;  fpt=_fpt; };

      virtual void operator()(const char* string)
       { (*pt2Object.*fpt)(string);};              // execute member function

      virtual void Call(const char* string)
        { (*pt2Object.*fpt)(string);};             // execute member function
   };

class TClassA{
   public:

      TClassA(){};
      void Display(const char* text) { cout << text << endl; };

      /* more of TClassA */
   };

   // dummy class B
   class TClassB{
   public:

      TClassB(){};
      void Display(const char* text) { cout << text << endl; };

      /* more of TClassB */
   };


   // main program
   int main(int /*argc*/, char* /*argv[]*/)
   {
      // 1. instantiate objects of TClassA and TClassB
      TClassA objA;
      TClassB objB;

  TSpecificFunctor<TClassA> specFuncA(&objA, &TClassA::Display);
  TSpecificFunctor<TClassB> specFuncB(&objB, &TClassB::Display);
  TFunctor* vTable[] = { &specFuncA, &specFuncB };
  vTable[0]->Call("TClassA::Display called!");        // via function "Call"
  (*vTable[1])   ("TClassB::Display called!");        // via operator "()"
   cout << endl << "Hit Enter to terminate!" << endl;
   cin.get();
   return 0;
   }

Now i tried to replace main() with a class

class test
{
public:
TClassA objA;

This is not possible now

TSpecificFunctor<TClassA> specFuncA(&objA, &TClassA::Display);
};

How to achieve this when main() is removed.

[xpi0t0s]

You always have to have a main function in C++; it's the starting point for your program.

[punith]

Quote:

Originally Posted by xpi0t0s

You always have to have a main function in C++; it's the starting point for your program.

But i need this to be a library and the main is present somewhere else
I tried to compile this piece of code with -c option

[xpi0t0s]

OK. What does "This is not possible" mean? Do you get an error?
If so, what is that error?
If not, please explain why you think it is not possible.

[punith]

Sorry for the confusion. I will add it properly this time .

This is my hdr file (hdr.h) file.

class TFunctor
   {
   public:

      // two possible functions to call member function. virtual cause derived
      // classes will use a pointer to an object and a pointer to a member function
      // to make the function call
      virtual void operator()(const char* string)=0;  // call using operator
      virtual void Call(const char* string)=0;        // call using function
   };


   // derived template class
   template <class TClass> class TSpecificFunctor : public TFunctor
   {
   private:
      void (TClass::*fpt)(const char*);   // pointer to member function
      TClass* pt2Object;                  // pointer to object

   public:

      // constructor - takes pointer to an object and pointer to a member and stores
      // them in two private variables
      TSpecificFunctor(TClass* _pt2Object, void(TClass::*_fpt)(const char*))
         { pt2Object = _pt2Object;  fpt=_fpt; };

      // override operator "()"
      virtual void operator()(const char* string)
       { (*pt2Object.*fpt)(string);};              // execute member function

      // override function "Call"
      virtual void Call(const char* string)
        { (*pt2Object.*fpt)(string);};             // execute member function
   };

This is my CPP file
[code]

#include "hdr.h"
#include <iostream>
using namespace std;

class TClassA{
   public:

      TClassA(){};
      void Display(const char* text) { cout << text << endl; };

      /* more of TClassA */
   };

   // dummy class B
   class TClassB{
   public:

      TClassB(){};
      void Display(const char* text) { cout << text << endl; };

      /* more of TClassB */
   };

class test
     27    {
     28       public:
     29 
     30       // 1. instantiate objects of TClassA and TClassB
     31       TClassA objA;
     32       TClassB objB;
     33 
     34 
     35       TSpecificFunctor<TClassA> specFuncA(&objA, &TClassA::Display);
};

I get this error while compiling

[root@localhost example]# g++ -c hdr.cpp 
hdr.cpp:35: error: expected identifier before ‘&’ token
hdr.cpp:35: error: expected identifier before ‘&’ token
hdr.cpp:35: error: expected ‘,’ or ‘...’
[root@localhost example]#

[xpi0t0s]

OK, so it looks like you've taken the code from main() and are trying to use it as a class definition.
This won't work; you need to write function code in functions, not in class definitions.
One way if the code must go in a class definition is to have a member function that contains the code from main; that should work OK.

class test {
public:
  void func() {
    TClassA objA;
    TClassB objB;
    TSpecificFunctor<TClassA> specFuncA(&objA, &TClassA::Display);
  }

[punith]

hi now it compiles. I was under the impression that

TSpecificFunctor<TClassA> specFuncA(&objA, &TClassA::Display);

is actually creating a member function specFuncA(..) under the class test.

[punith]

thanks for replying xpi0t0s now it works for me