how can I split the header and the Implementation by overloading operator

Question

am learning C++ coming from java world as a middle-range developer...

now am trying to learn how to do operator overloading

even tho I searched a lot in the web and SO:

How to properly overload the << operator for an ostream?

https://stackoverflow.com/a/476483/982161

this here is my reference:

the give this example:

// overload_date.cpp  
// compile with: /EHsc  
#include <iostream>  
using namespace std;  

class Date  
{  
    int mo, da, yr;  
public:  
    Date(int m, int d, int y)  
    {  
        mo = m; da = d; yr = y;  
    }  
    friend ostream& operator<<(ostream& os, const Date& dt);  
};  

ostream& operator<<(ostream& os, const Date& dt)  
{  
    os << dt.mo << '/' << dt.da << '/' << dt.yr;  
    return os;  
}  

int main()  
{  
    Date dt(5, 6, 92);  
    cout << dt;  
}

But I want/need to develop this using the separation of headers and implementation

my Code

Header

#ifndef POINT_H
#define POINT_H
#include <ostream>

class Point
{
    public:
        Point();
        virtual ~Point();

        unsigned int Getx();
        unsigned int Gety();

        void Setx(unsigned int val);
        void Sety(unsigned int val);
        friend std::ostream& operator<<(std::ostream& ostream, const Point& dt);

    private:
        unsigned int x;
        unsigned int y;
};
#endif // POINT_H

Implementation

#include "Point.h"
#include <ostream>

Point::Point()
{
     x = 1u;
     y = 1u;
}

Point::~Point()
{
    //dtor
}

unsigned int Point::Getx()
{
     return x;
}

unsigned int Point::Gety()
{
    return y;
}

void Point::Setx(unsigned int val)
{
     x = val;
}

void Point::Sety(unsigned int val)
{
     y = val;
}

std::ostream& operator<<(std::ostream& out, const Point& a) {
    return out << "A(" << a.Getx() << ", " << a.Gety() ")";
}

I can not compile teh code getting this error:

include\Point.h|24|error: passing 'const Point' as 'this' argument of 'unsigned int Point::Getx()' discards qualifiers [-fpermissive]|

Why? A getter should always be const since it doesn't modify the object, a setter does. — SingerOfTheFall, Apr 04 '17 at 11:19
Oh... thanks! @SingerOfTheFall, so removing the const keyword must be the solution...?? — Firewall-Alien, Apr 04 '17 at 11:21
Why is the destructor `virtual`? What class invariants do your getters and setters protect? None? Then why do you have them? Please don't write Java with C++ syntax, you will get bad code. Approach C++ as learning a new language instead, don't blindly try to apply principles from other languages to C++. — Baum mit Augen, Apr 04 '17 at 11:22
*"so removing the const keyword must be the solution...?? "* That's exactly what I'm talking about. Stop guessing, read a book. — Baum mit Augen, Apr 04 '17 at 11:23
@BaummitAugen am not guessing, this class was generated by a Codeblock Wizard..... so have no idea why the wizard suggest that destructor should be virrtual — Firewall-Alien, Apr 04 '17 at 11:42
@Firewall-Alien I don't know that tool, but you evidently should not blindly use the output of some source generation tool you don't understand either, as that example in the question illustrates. — Baum mit Augen, Apr 04 '17 at 11:46

score 0 · Answer 1 · answered Apr 04 '17 at 11:58

Two things to make your code compile:

First: Your getters should be const.

unsigned int Getx() const;
unsigned int Gety() const;

unsigned int Point::Getx() const
{
   return x;
}

unsigned int Point::Gety() const
{
   return y;
}

Second:

Correct the return on your overridden method:

return out << "A(" << a.Getx() << ", " << a.Gety() << ")";

(You were missing the last "<<").

how can I split the header and the Implementation by overloading operator

Header

Implementation

1 Answers1