C++ Cycle through the addresses of an object

Question

Objects (that are not dynamic) are blocks of data in memory.

Is there a way to cycle through and print each item in an object?

I tried doing it with 'this' but I keep getting errors.

#include "stdafx.h"
#include <iostream>
#include "TestProject.h"

using namespace std;


class myclass {

    int someint = 10;
    double somedouble = 80000;
    int somearray[5] = {0, 1, 2, 3, 4};


public:   
    void somefunction();


};


void myclass::somefunction() {


    cout << "\n test \n" << this;

    myclass *somepointer;

    somepointer = this; 

    somepointer += 1;

    cout << "\n test2 \n" << *somepointer;
    //Error: no opperator '<<' matches these operands

}



int main() {


    myclass myobject;

    myobject.somefunction();

    return 0;
}

I'm guessing the error is because the types don't match. But I can't really figure a solution. Is there a dynamic type, or do I have to test the type somehow?

Answer 1

You must add friend global std::ostream operator << to display content of object

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

using namespace std;


class myclass {
    int someint;
    double somedouble;
    int somearray[5];
public: 
    myclass()
    {
        someint = 10;
        somedouble = 80000;
        somearray[0] = 0;
        somearray[1] = 1;
        somearray[2] = 2;
        somearray[3] = 3;
        somearray[4] = 4;
    }
    void somefunction();
    friend std::ostream& operator << (std::ostream& lhs, const myclass& rhs);
};


std::ostream& operator << (std::ostream& lhs, const myclass& rhs)
{
    lhs << "someint: " << rhs.someint << std::endl
        << "somedouble: " << rhs.somedouble << std::endl
        << "somearray: { ";

    for (int iIndex = 0; iIndex < 5; iIndex++)
    {
        if (iIndex == 4)
            lhs << rhs.somearray[iIndex] << " }" << std::endl;
        else
            lhs << rhs.somearray[iIndex] <<  ", ";
    }

    return lhs;
}


void myclass::somefunction() {


    cout << "\n test \n" << this;

    myclass *somepointer;

    somepointer = this; 

    somepointer += 1; // wrong pointer to object with `object + sizeof(object)` address, 
    // data probably has been corrupted

    cout << "\n test2 \n" << *somepointer; // displaying objects content
}

int main() {


    myclass myobject;

    myobject.somefunction();

    return 0;
}

as you want to get to the object member using its pointers shifts I post another program

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

using namespace std;


#pragma pack (push, 1) // force data alignment to 1 byte

class myclass {
    int someint;
    double somedouble;
    int somearray[5];
public: 
    myclass()
    {
        someint = 10;
        somedouble = 80000;
        somearray[0] = 0;
        somearray[1] = 1;
        somearray[2] = 2;
        somearray[3] = 3;
        somearray[4] = 4;
    }
    void somefunction();
    friend std::ostream& operator << (std::ostream& lhs, const myclass& rhs);
};

#pragma pack (pop) // restore data alignment


std::ostream& operator << (std::ostream& lhs, const myclass& rhs)
{
    lhs << "someint: " << rhs.someint << std::endl
        << "somedouble: " << rhs.somedouble << std::endl
        << "somearray: { ";

    for (int iIndex = 0; iIndex < 5; iIndex++)
    {
        if (iIndex == 4)
            lhs << rhs.somearray[iIndex] << " }" << std::endl;
        else
            lhs << rhs.somearray[iIndex] <<  ", ";
    }

    return lhs;
}


void myclass::somefunction() {

    int* pSomeInt = (int*)this; // get someint address
    double *pSomeDouble = (double*)(pSomeInt + 1); // get somedouble address
    int* pSomeArray = (int*)(pSomeDouble + 1); // get somearray address

    std::cout << "someint: " << *pSomeInt << std::endl
        << "somedouble: " << *pSomeDouble << std::endl
        << "somearray: { ";

    for (int iIndex = 0; iIndex < 5; iIndex++)
    {
        if (iIndex == 4)
            std::cout << pSomeArray[iIndex] << " }" << std::endl;
        else
            std::cout << pSomeArray[iIndex] <<  ", ";
    }
}

int main() {


    myclass myobject;

    myobject.somefunction();

    return 0;
}