Question

I got three .cpp files and two header files.

But when i compile them, meaning the Point.cpp, Data.cpp and main.cpp, it will say

Data.h:6:7 redefinition of Data at 'Data.h'
Data.h:6:7 previously definition of 'class Data'

Below is my Data.h(previously known as 2.h at above)

#include <iostream>
#include <string>

using namespace std;

class Data
{
private:
string sType;
public:
Data();
Data(string);
void setSType(string);
string getSType();
};

Below is my data.cpp

#include "Data.h"

Data::Data()
{
sType = "";
}

Data::Data(string s)
{
sType = s;
}

void Data::setSType(string ss)
{
sType = ss;
}

string Data::getSType()
{
return sType;
}

Below is my PointD.h (previously known as 3.h)

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

using namespace std;

class PointD
{
private:
int x
Data data1;
public:
PointD();
PointD(int,Data);

void setX(int);
void setData(Data);

int getX();
Data getData();
};

Below is my PointD.cpp

#include "PointD.h"

PointD::PointD()
{
x = 0;
}

PointD::PointD(int xOrdinate,Data dd)
{
x = xOrdinate;
data1 = dd;
}

void PointD::setXordinate(int Xordinate)
{
x = Xordinate;
}

void PointD::setData(Data dd)
{
data1 = dd;
};

int PointD::getXordinate()
{
return x;
}

Data PointD::getData()
{
return data1;
}

This is my main.cpp

#include <iostream>
#include <string>

#include "Data.h"
#include "PointD.h"
using namespace std;

int main()
{
const int MAX_NUM = 20;

Data ldata[MAX_NUM];
PointD pointd[MAX_NUM];

//more codes..
}

But when i compile them, meaning the Point.cpp, Data.cpp and main.cpp, it will say

Data.h:6:7 redefinition of Data at 'Data.h'
Data.h:6:7 previously definition of 'class Data'

Can anybody let me know whats actually went wrong here..

Answer 1

You need to use include guards, or the easiest:

 #pragma once

in your header files

See Purpose of Header guards for more background

Idea: 1.hpp

#ifndef HEADER_GUARD_H1_HPP__
#define HEADER_GUARD_H1_HPP__

// proceed to declare ClassOne

#endif // HEADER_GUARD_H1_HPP__