错误：重新定义 Class (C++)

Question

I'm trying to figure out why I'm getting the following error:

error: redefinition of 'TimeDuration'

// TimeDuration.cpp

#define HOUR 3600
#define MIN 60

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

using namespace std;

TimeDuration::TimeDuration() {
    seconds = 0;
}

void TimeDuration::setDuration(const int sec) {
    seconds = sec;
}

void TimeDuration::display() {
    // Some code to display the time
}

The error is showing in my header file.

// TimeDuration.h

class TimeDuration {
    private:
        int seconds;
    public:
        TimeDuration();                     
        void setDuration(const int sec);    
        void display();                     
};

Answer 1

The error is probably because you don't have header guards in TimeDuration.h

A standard way to header guard is to at the beginning of the file write:

#ifndef TIME_DURATION_H
#define TIME_DURATION_H

and at the end of the file:

#endif

Answer 2

you can use

#pragma once

in your TimeDuration.h file, at the starting