Question

I know it’s frequently asked question but I can’t figure out a way for my code to work, so I’ll be glad to get some help.Here’s the code:

#include "stdafx.h"
#include "iostream"
#include "string"
#include "cmath"
#include "ctime"
using namespace std;
class quad{
    int Lice;
public:
    quad(int x, int z){
       Lice = x*z;
    }
    int ShowLice(){
        return Lice;
    }
};
class tri : public quad{
    int Lice;
public:
    tri(int a, int b, int c){
        Lice = a*b*c;
    }

};
int main(){
quad ob1(2,2);
tri ob2(2,2,2);
cout<<ob1.ShowLice();
cout<<ob2.ShowLice();

return 0;
}

I use VS2008 and the error from the compiler is :

project1.cpp(20) : error C2512: 'quad' : no appropriate default constructor available

Thanks, Leron.

Answer 1

Change it to

class quad{
protected:
    int Lice;
public:
    quad(int x, int z){
       Lice = x*z;
    }
    int ShowLice(){
        return Lice;
    }
};
class tri : public quad{

public:
    tri(int a, int b, int c) : quad(a,b) {
        Lice *= c;
    }

};

No point in having a Lice member in both derived and base class. Make it protected so that both derived and child classes reuse the same field.

If you have a non default constructor in base class you have to invoke the base class constructor with the right arguments from the derived class constructor like i have shown above.

Also if you use inheritance it is a good idea to provide a virtual destructor in base class. The problem might not be apparent in your example code.