Question

I have encountered an error which has stumped me for many days now. A quick google hasn’t given me an answer. The code, to my eyes, has no errors however when I run the program I get 9 Unresolved External Symbol(LNK2019) error. After trying to decipher one of my errors, I believe it is happening in a function named createMortgage. Here is my calling of the function.
customers is a Vector.

for (unsigned int i = 0; i < customers.size(); i++)
            {
                Customer tempcust = customers.at(i);
                if (tempcust.getId() == id)
                {
                    customers.at(i).createMortgage();
                }
            }

Here is the function itself.

void createMortgage(){
        int amount;

        cout << "Amount?";
        cin >> amount;

        Mortgage mort(amount);
        mortgages.push_back(mort);
    }

And here, in all it’s glory, is the error.

Error   4   error LNK2019: unresolved external symbol "public: __thiscall Mortgage::Mortgage(double)" (??0Mortgage@@QAE@N@Z) referenced in function "public: void __thiscall Customer::createMortgage(void)" (?createMortgage@Customer@@QAEXXZ) F:\C++ assignment (Real)\C++ assignment (Real)\Driver.obj   C++ assignment (Real)

Here is my mortgage .h file.

#pragma once
//#include <iostream>
//#include <String>

class Mortgage
{

private:
    int id;
    double amount;

public:
    Mortgage(double amount);
    double getAmount();
    int getId();
};

And here is my mortgage .cpp file.

#pragma once

extern int idcreation;

class Mortgage
{

    int id;
    double amount;

    Mortgage(double amount)
    {
        this -> amount = amount;
        this -> id = idcreation;
        idcreation++;
    }

    int getId(){
        return id;
    }

    double getAmount(){
        return amount;
    }

Answer 1

Change this:

class Mortgage
{
int id;
double amount;

Mortgage(double amount)
{
    this -> amount = amount;
    this -> id = idcreation;
    idcreation++;
}

int getId(){
    return id;
}

double getAmount(){
    return amount;
}

To this:

#include "mortgage.h"

Mortgage::Mortgage(double amount)
{
    this -> amount = amount;
    this -> id = idcreation;
    idcreation++;
}

int Mortgage::getId(){
    return id;
}

double Mortgage::getAmount(){
    return amount;
}

I see you don’t really get how to use headers and source files to make classes, this tutorial will get you on track: http://thenewboston.org/watch.php?cat=16&number=15.