Question

Please have a look at the following code

Location.h

#pragma once
class Location
{
public:
    Location(void);
    Location(int,int,int);
    ~Location(void);
    Location(const Location *loc);

    void display();
    void set(int,int,int);

private:

    int x,y,z;
};

Location.cpp

#include "Location.h"
#include <iostream>
#include <string>

using namespace std;


Location::Location()
{
}

Location::Location(int x,int y, int z)
{
    set(x,y,z);
}



Location::~Location(void)
{
}


void Location::display()
{
    cout << "X: " << x << endl;
    cout << "Y: " << y << endl;
    cout << "Z: " << z << endl;
}

void Location::set(int xx,int yy,int zz)
{
    x = xx;
    y = yy;
    z = zz;
}

Object.h

#pragma once
#include "Location.h"

class GameObject
{
public: 
    GameObject(int);
    ~GameObject(void);
    GameObject(int,Location *);
    GameObject(const GameObject *obj);

    Location *location;

    int getNumberOfObjects();

    static int counter;


    int id;

private:
    GameObject(void);



};

Object.cpp

#include "GameObject.h"
#include <iostream>

using namespace std;

static int counter = 0;

int GameObject::counter = 0;

GameObject::GameObject(void)
{
}

GameObject::GameObject(int i)
{
    counter++;
    id = i;
}

GameObject::GameObject(int i,Location *loc)
{
    id = i;
    location = loc;
}

GameObject::GameObject(const GameObject *ob)
{
    this->location = new Location(ob->location);
}


GameObject::~GameObject(void)
{
}

Main.cpp

#include <iostream>
#include "GameObject.h"

using namespace std;

int main()
{
    //GameObject obj1;
    //cout << obj1.id << endl;

    GameObject obj2(45);
    cout << obj2.id << endl;;
//  cout << obj2.counter << endl; 

    //Declaring dynamic objects for Location
    Location *loc1 = new Location(1,1,1);
    Location *loc2 = new Location(2,2,2);
    Location *loc3 = new Location(3,3,3);


    //Assigning each GameObject a location
    GameObject obj3(45,loc1);
    GameObject obj4(45,loc2);
    GameObject obj5(45,loc3);

    //Displaying Number of GameObject objects
    cout << "Number of Objects: " << GameObject::counter << endl;

    //Invoking Location's display() method using GameObject objects
    cout << "......obj3 values........" << endl;
    obj3.location->display();
    cout << "......obj4 values........" << endl;
    obj4.location->display();
    cout << "......obj5 values........" << endl;
    obj5.location->display();


    //Declaring new Static GameObject
    GameObject obj6(obj4);

    //Invoking display() member function using both obj4 and obj6 GameObjects
    cout << endl;
    cout << "Invoking display() member function using both obj4 and obj6 GameObjects " << endl;
    obj4.location->display();
    obj6.location->display();

    //Changing the location values in obj4
    obj4.location->set(8,8,8);

    //Invoking display() member function using both obj4 and obj6 GameObjects
    cout << endl;
    cout << "Invoking display() member function using both obj4 and obj6 GameObjects " << endl;
    obj4.location->display();
    obj6.location->display();




    system("pause");
    return 0;
}

In here, as you can see in Main.cpp, obj6 ‘Location’ has been changed as soon as obj4 ‘Location’ is changed. I don’t want to change the obj6 ‘Location’ when I change the location for obj4.

I get this error when this is executed

GameObject.obj : error LNK2019: unresolved external symbol "public: __thiscall Location::Location(class Location const *)" (??0Location@@QAE@PBV0@@Z) referenced in function "public: __thiscall GameObject::GameObject(class GameObject const *)" (??0GameObject@@QAE@PBV0@@Z)

I tried to do it with a deep copy constructor, but it didn’t work. Please help.

Answer 1

GameObject::GameObject(const GameObject *ob)

is not the copy constructor, You need:

GameObject::GameObject(const GameObject &ob)
                                       ^^^

Also, you need to provide a copy assignment operator which does a deep copy.

Note that the ideal solution is to use smart pointer as member instead of an raw pointer.
This shall basically save you all the hassles of deep copying.

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Good Read:
What is The Rule of Three?