Question

In c++ I want to have an array of the abstract type Query which has the function calcScore()
which is a pure virtual function.
And I have two classes which are non-abstract: ConQuery and DisQuery that implements the calcScore function.

In order to do I defined the array like this:

vector<Query*> m;

and I iterate and call the function like this:

for (vector<Query*>::const_iterator it1 = index.begin() ;it1 != index.end() ; it1++)
{
     cout << (*it1)->CalcScore() << endl; 
}

I get an error for calling a pure virtual function of Query.
How do I make it call to the function of ConQuery or the one of DisQuery by the polymorphic type?
thanks.

Answer 1

Are you sure CalcScore is implemented in ConQuery and DisQuery ?
I tried this:

#include <iostream>
#include <vector>

class Query{
public:
    virtual int CalcScore() = 0;
};

class Query2 : public Query
{
public:
    virtual int CalcScore()
    {

        return 2;
    }
};

class Query3 : public Query
{
public:
    virtual int CalcScore()
    {

        return 3;
    }
};

int main(int argc, char* argv[])
{

    std::vector<Query*> m;
    m.push_back(new Query2());
        m.push_back(new Query3());
    for (std::vector<Query*>::const_iterator it1 =  m.begin() ;it1 !=  m.end() ; it1++)
    {
        std::cout  << (*it1)->CalcScore();
    }
}

and it works fine under my VS2012.

Also I used it tons of times in some of my projects.

Maybe you try to push_back a Query item ( and not a con/dis ) ?