Only the first derived class is being included - c++

Question

I'm new to C++, and for a school assignment we have to create a base class and create 2 derived classes from it, then display the output of all the associated functions of the two derived classes.
The problem is, when I try to include the two derived classes in my test file, only the one that I include first works. If I reverse the order that I include them, then the one that's now included first works, but the second one doesn't
Any ideas why this might be happening?
Here's my test file:
#include "Payment.h"
#include "CashPayment.h" // This one will work
#include "CreditCardPayment.h" // This one won't. Unless you switch them
#include <iostream>
#include <string>
using namespace std;
// Tests the CashPayment and CreditCardPayment classes, derived from the Payment clas
int main() {
CashPayment firstCash(420);
cout << "First Cash Payment" << endl
<< "Amount: " << firstCash.getAmount() << endl
<< firstCash.paymentDetails() << endl;
CreditCardPayment firstCredit("Mingwu Chen", 123456789, 11, 2016, 100);
cout << "Number: " << firstCredit.getNumber() << endl
<< "Month: " << firstCredit.getMonth() << endl
<< "Year: " << firstCredit.getYear() << endl
<< "Amount: " << firstCredit.getAmount() << endl
<< firstCredit.paymentDetails() << endl;
}
Here's my CashPayment.h file:
#ifndef CASHPAYMENT_H
#define CASHPAYMENT_H
#include <string>
#include "Payment.h"
using namespace std;
class CashPayment: public Payment {
public:
// Creates a CashPayment with an amount of 0
CashPayment();
// Creates a CashPayment with the given amount
CashPayment(double a);
// Creates a string out of all the CashPayment details
string paymentDetails();
};
#endif
Here's the CreditCardPayment.h file:
#ifndef CASHPAYMENT_H
#define CASHPAYMENT_H
#include <string>
#include "Payment.h"
using namespace std;
class CreditCardPayment: public Payment {
private:
string name;
int cardNumber;
int expMonth;
int expYear;
public:
// Creates a CreditCardPayment with an amount of 0
CreditCardPayment();
// Creates a CreditCardPayment with the given card holder name, card number, expiry month, expiry year, and amount
CreditCardPayment(string n, int c, int m, int y, double a);
// Creates a string out of all the CreditCardPayment details
string paymentDetails();
// Returns the card holder name
string getName();
// Returns the card number
int getNumber();
// Returns the expiry month
int getMonth();
// Returns the expiry year
int getYear();
// Sets the card holder name t0 the given name
void setName(string n);
// Sets the card number to the given number
void setNumber(int c);
// Sets the expiry month to the given month
void setMonth(int m);
// Sets the expiry year to the given year
void setYear(int y);
};
#endif
Here's the Payment.h file:
#ifndef PAYMENT_H
#define PAYMENT_H
#include <string>
using namespace std;
class Payment {
private:
double amount;
public:
// Creates a Payment with an amount of 0
Payment();
// Creates a Payment with the given amount
Payment(double a);
// Returns the amount
double getAmount();
// Sets the amount to the given value
void setAmount(int a);
// Creates a string out of all the Payment details
string paymentDetails();
};
#endif
I've been up all night trying to figure this out, and I'm offically stumped. Any ideas or suggestions at all with be greatly appreciated.
(PS: Many people on here don't seem to like using namespace std, but that's what my teacher wants)

Answer 1

Both header files have:
#ifndef CASHPAYMENT_H
#define CASHPAYMENT_H
As such, whichever one is included first, is the one whose contents actually get compiled.

Answer 2

#ifndef CASHPAYMENT_H
#define CASHPAYMENT_H
(stuff)
#endif
This is called the include-guard, and it stops a file being included more than once when the program is compiled.
You shouldn't have CASHPAYMENT_H on all three header files - each file needs a unique include-guard. It doesn't actually matter what, as long as it's unique in your project, and the header filename in uppercase is a good convention for this.
As an alternative to #ifndef, you can use #pragma once, which does the same thing:
#pragma once
(stuff)
(Note there's no #endif at the end of the file.)
It's not in the C++ standard but it's supported by pretty much all of the compilers and is a bit clearer.

Answer 3

In the CreditCardPayment.h file put this:
#ifndef CREDITCARDPAYMENT_H
#define CREDITCARDPAYMENT_H

Answer 4

You must copy your code, it is better to build your class from a tool in your IDE. That will automatically add the header defender for you. And your payment detail function should be virtual.