CODEWITHSUNDEEP
c++
Stahp
Stahp

Reputation: 1150

Constructor can't access inherit class private int

Class Point is working correctly, It is creating x, y point. Code:

point.h file

#ifndef POINT_H
#define POINT_H

namespace pt
{
    class Point
    {
        int x, y;
    public:
        Point();
        Point(int x, int y);
        int getX();
        int getY();
    };
}
#endif // POINT_H

point.cpp file

#include "point.h"

pt::Point::Point()
{
    this->x = this->y = 0;
}

pt::Point::Point(int x, int y)
{
    this->x=x;
    this->y=y;
}

int pt::Point::getX()
{
    return this->x;
}

int pt::Point::getY()
{
    return this->y;
}

Meanwhile when I try to create new Point3D class in main that will inherit from Point x, y coordinates and add z to create third dimension, new constructor cant get access to x, y of Point class. Errors are: 1. 'int pt::Point::x' is private at first and second this-> in Point3D constr. 2. Both are 'out of context'

main.cpp

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

int main()
{
    class Point3D : public pt::Point
    {
        int z;
    public:
        getZ()
        {
            return this->z;
        }

        Point3D(int x ,int y, int z)
        {
            this->x=x;
            this->y=y;
            this->z=z;
        }
    };
    return 0;
}

Thanks for help.

Upvotes: 0

Views: 128

Answers (1)

Olivier Sohn
Olivier Sohn

Reputation: 1322

To make x and y accessible to derived classes, you should make them protected:

class Point
{
protected:
    int x, y;
public:
    Point();
    Point(int x, int y);
    int getX();
    int getY();
};

By default, the visibility of a class member is private (note that this is different from the struct default where a struct member is public by default). On that topic, see this answer.

And as a side note, the idiomatic way to initialize x and y would be to write:

Point3D(int x ,int y, int z) : pt::Point(x,y)
{
    this->z=z;
}

Then, you don't need to make x and y protected, they can remain private.

You can even write it like that:

Point3D(int x ,int y, int z) : pt::Point(x,y), z(z)
{}

Upvotes: 2

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