c++ no virtual function found on table

[OninO]

Hello

i'm trying to create a vector list using the STL lib.
the first method works but the second crashes cause: virtual function _Build () not found on table.
What's wrong?
Compiled with gcc.

code:

//// Main
#include <iostream>
#include "TOcc.h"
#include "TColl.h"

#include <vector>

using namespace std;

int main()
{

DBE dbe;

cout << endl << " Method 1. it work!" << endl;

vector<_TOccV<DBE> *> list;

_TOccV<DBE> *p;

TOcc1 s1;
p = &s1;
list.push_back(p);

TOcc2 s2;
p = &s2;
list.push_back(p);

list[0]->Build ();
list[1]->Build ();

cout << endl << " Method 2. Don't work" << endl;

TColl list2;

list2.BuildAll ();

return 0;
}



codice:

///// TOcc.h
#ifndef TOCC_H_INCLUDED
#define TOCC_H_INCLUDED

#include<assert.h>
#include<vector>

using namespace std;

class DBE {

vector<int> someData;

public:

DBE () {};

};



template <typename S>
class _TOccV {

vector< vector<int> > *_data;
int _dataYSize;

virtual void _Build (void) { cout << endl << "_TOccV::_Build" << endl; };

public:

_TOccV () : _dataYSize(0) { };
_TOccV (int dataYSize) : _dataYSize(dataYSize)
{ _data = new vector< vector<int> >(dataYSize); };
~_TOccV ()
{ delete _data; _data = NULL; };

void Push (vector<int> *v, int where) { _data[where].push_back(*v); };
vector<int> Pop (int what) { assert(what < _data->size()); return (*_data)[what]; };
void Build (void) { _Build (); };

};


class TOcc1 : public _TOccV<DBE> {

void _Build (void) { cout << endl << "TOcc1::_Build" << endl; };

public:

TOcc1 () : _TOccV<DBE> (1) {};

};


class TOcc2 : public _TOccV<DBE> {

void _Build (void) { cout << endl << "TOcc2::_Build" << endl; };

public:

TOcc2 () : _TOccV<DBE> (1) {};

};

#endif // TOCC_H_INCLUDED


/////// TColl.h
#ifndef TCOLL_H_INCLUDED
#define TCOLL_H_INCLUDED

#include <vector>
#include "TOcc.h"

using namespace std;

class TColl {

vector<_TOccV<DBE> *> _list;

public :

TColl ();

void BuildAll (void);

};



TColl::TColl ()
{

_TOccV<DBE> *p;

TOcc1 s1;
p = &s1;
_list.push_back(p);

TOcc2 s2;
p = &s2;
_list.push_back(p);

};


void TColl::BuildAll (void)
{
unsigned int idx;
_TOccV<DBE> *p;

for (idx = 0; idx < _list.size(); idx++)
{
p = _list[idx];
p->Build ();
}

}


#endif // TCOLL_H_INCLUDED

[TheRogue]

TColl::TColl ()
{

_TOccV<DBE> *p;

TOcc1 s1;
p = &s1;
_list.push_back(p);

TOcc2 s2;
p = &s2;
_list.push_back(p);

};

Ask yourself what happens to s1 and s2 when the constructor is complete.

[OninO]

maybe s1 and s2 will be destroyed?

[TheRogue]

Yup
If they get destroyed, then anything pointing to them will now be invalid.

[OninO]

ok, i understand...

i just resolve it declaring s1 and s2 static in a new init() function:

void TColl::init (void)
{

_TOccV<DBE> *p;

static TOcc1 s1;
p = &s1;
_list.push_back(p);

static TOcc2 s2;
p = &s2;
_list.push_back(p);

};

now works but i'm not sure is the right way.

[laserlight]

It probably is not the right way. I suggest that you use a vector<std::tr1::shared_ptr<_TOccV<DBE> > > or a boost:tr_vector<_TOccV<DBE> >, with _list.push_back(new TOcc1<DBE>()).

By the way, names that begin with an underscore followed by an uppercase letter, or that contain consecutive underscores, are reserved to the implementation for any use. Therefore, rename _TOccV (its name is rather cryptic anyway).

[OninO]

i think the syntax is:

vector<std::tr1::shared_ptr<_TOccV<DBE> > > _list2; // list declaration

_list2.push_back(std::tr1::shared_ptr<_TOccV<DBE> > (new TOcc1)); // insertion

_list2[what].Build () // access to function member

right?

[monarch_dodra]

i think the syntax is:

vector<std::tr1::shared_ptr<_TOccV<DBE> > > _list2; // list declaration

_list2.push_back(std::tr1::shared_ptr<_TOccV<DBE> > (new TOcc1)); // insertion

_list2[what]->Build () // access to function member

right?

Pretty much, the objects in your vector are pointers, so use "->" not "."

I recommend you use typdefs:

typedef _TOccV<DBE> toc_dbe_t;
typedef std::tr1::shared_ptr<toc_dbe_t> smart_toc_dbe_t;

vector<smart_toc_dbe_t> myContainer;
myContainer.push_back(smart_toc_dbe_t(new toc_dbe_t));
myContainer->Build();

I have no idea what you are doing, so my names are not the best, but you get the point.

By the way, _list2 is a terrible name. For starters, a list is a very precise object in C++, of which _list2 is not a type (it is a vector). Also, avoid numbering your variables. The name should contain a good description of the variable. "2" is not very descriptive.

[OninO]

Pretty much, the objects in your vector are pointers, so use "->" not "."

right. i did it!

I recommend you use typdefs:

typedef _TOccV<DBE> toc_dbe_t;
typedef std::tr1::shared_ptr<toc_dbe_t> smart_toc_dbe_t;

vector<smart_toc_dbe_t> myContainer;
myContainer.push_back(smart_toc_dbe_t(new toc_dbe_t));
myContainer->Build();

thanks! much readable than my code

I have no idea what you are doing, so my names are not the best, but you get the point.

By the way, _list2 is a terrible name. For starters, a list is a very precise object in C++, of which _list2 is not a type (it is a vector). Also, avoid numbering your variables. The name should contain a good description of the variable. "2" is not very descriptive.

i always use underscore for the private members of my classes. maybe this is not a good way... i will try to dont do it
i used _list cause before using vector i tried with a list. :-) 2 because _list was commented (the first and wrong version of _list2) :-)

thank you!