Way to handle the objects in C++

Question

Every time when I run the code Compiler give the error of object already define and I don't know where I am making mistakes in the whole code.

Even if I do this all in one file it is working but I don't know why its not working in this style can anyone help me that where I am doing mistake in this code.

Any help would be appreciated. Thank you

student.h

ifndef STUDENT
define STUDENT

class Student
{

public:
    char student_no[10];
    char student_name[20];
    char student_address[20];
    char student_score[20];
    Student();

};

Student::Student()
{//constructor
    student_no[0] = 0; student_name[0] = 0; student_address[0] = 0;
    student_score[0] = 0;
}

#endif

student.cpp

using namespace std;
#include "writestr.cpp"
#include <fstream>
#include <string.h>
#include <iostream>



int main(){
    char filename[20];
    Student s;
    cout << "Enter the file name:" << flush;
    cin.getline(filename, 19);
    ofstream stream(filename, ios::out);
    if (stream.fail()) {
        cout << "File open failed!" << endl;
        return 0;
    }
    while (1) {
        cin >> s; // read fields of person
        if (strlen(s.student_name) == 0) break;
        // write person to output stream
        stream << s; // write fields of person
    }
    return 1;
}

Problems occured

This is the portion where I write the streaming code.

writestr.cpp

using namespace std;
#include "readper.cpp"
#include <fstream>
#include <string.h>
#include <iostream>

ostream & operator << (ostream & stream, Student & s)
{ // insert fields into file
    stream << s.student_name << s.student_no << s.student_address
        << s.student_score;
    return stream;
}

readper.cpp

using namespace std;
#include "student.h"
#include <fstream>
#include <string.h>
#include <iostream>   
istream & operator >> (istream & stream, Student & s)
{ // read fields from input
    cout << "Enter Student Name, or <cr> to end: " << flush;
    stream.getline(s.student_name, 30);

    if (strlen(s.student_name) == 0) return stream;
    cout << "Enter Student Name: " << flush; stream.getline(s.student_name, 30);
    cout << "Enter Student Id Number: " << flush; stream.getline(s.student_no, 30);
    cout << "Enter Address: " << flush; stream.getline(s.student_address, 30);
    cout << "Enter Score: " << flush; stream.getline(s.student_score, 15);

    return stream;
}

Answer 1

You are defining (not just declaring) the constructor in the header file:

Student::Student()
{//constructor
    student_no[0] = 0; student_name[0] = 0; student_address[0] = 0;
    student_score[0] = 0;
}

This defines the constructor (generates the code) again and again in every cpp that includes the header file. Since this definition has no inline keyword, it may exist exactly once in the program, not multiple times. Defining the non-inline constructor in multiple translation units (cpp files) causes the error.

Possible solutions:

1. Move the constructor definition into the class, or
2. Prefix it by an inline keyword, or
3. Move it to one of the cpp files

Another issue: you include cpp files, which cause a lot more issues by declaring the same thing again and again. Simply add them to the project/makefile/etc, instead of including:

#include "writestr.cpp"