class pointer method crashing program - c++

Question

I am trying to make a program that has two account balances, one for a go-card the other for a bank account. I have made a class for each, however when I try to call the debit method in the go-card class via a class pointer, my program crashes (it compiles with no errors).
The GoCardAccount.cpp file:
#include <cstdio>
#include "GoCardAccount.hpp"
#include "BankAccount.hpp"
GoCardAccount::GoCardAccount(long initialamount, BankAccount(ba)) {
balance = initialamount;
}
bool GoCardAccount::trip(long amount) {
LOW_LIMIT = 1000;
TOP_UP = 5000;
if(balance >= amount) {
balance -= amount;
if(balance < LOW_LIMIT) {
if(ba->debit(TOP_UP)) {
printf("Balance fallen below minimum, "
"topped up $50 to go card account.\n");
balance += TOP_UP;
return true;
}
else {
printf("Your balance has gone below minimum amount, however "
"there are insufficient funds in bank account to top up.\n");
return true;
}
}
}
else {
return false;
}
}
long GoCardAccount::getBalance() {
return balance;
}
GoCardAccount.hpp file:
class BankAccount;
class GoCardAccount {
long balance;
BankAccount *ba;
long LOW_LIMIT;
long TOP_UP;
public:
GoCardAccount(long amount, BankAccount(ba));
bool trip(long amount);
long getBalance();
};
The debit method from BankAccount.cpp:
bool BankAccount::debit(long amount1) {
if(amount1 >=0 && amount1 <= balance) {
balance -= amount1;
return true;
}
else {
return false;
}
}
The start of the main function where I initialise the classes:
int main(void) {
long startamount;
long gocardamount;
printf("Input initial bank balance: \n");
scanf("%ld", &startamount);
BankAccount ba(startamount);
printf("Input initial Go-Card balance: \n");
scanf("%ld", &gocardamount);
GoCardAccount gca(gocardamount, ba);
}

Answer 1

For first let's talk about your constructor of class GoCardAccount, because there is a term used by Scott Meyers in Effective STL (2001) book, which is the most vexing parse:
GoCardAccount(long amount, BankAccount(ba));
The code snippet above will declare a constructor which takes two parameters:
The long amount parameter is named amount, and it's type is long. This is fine.
The BankAccount(ba) parameter is named ba, and it's type is BankAccount, because the parentheses around ba are superfluous and are ignored.
So, the declaration above is same as:
GoCardAccount(long amount, BankAccount ba);
This isn't what you want, because the second parameter will take a BankAccount instance by value and you need a pointer to it. So, you have to change it to:
GoCardAccount(long amount, BankAccount* ba);
Change its definition as well and initialize your BankAccount* ba member as follows (or use the member initializer list):
GoCardAccount::GoCardAccount(long initialamount, BankAccount* ba_ptr) {
balance = initialamount;
ba = ba_ptr;
}

Answer 2

Now you are trying to call ba method, but BankAccount *ba; is not even itinialized.
You have to pass a pointer on BankAccount to GoCardAccount ctor. So change this line (in main)
GoCardAccount gca(gocardamount, ba);
to
GoCardAccount gca(gocardamount, &ba);
and in GoCardAccount (GoCardAccount.cpp) change ctor from
GoCardAccount::GoCardAccount(long initialamount, BankAccount(ba))
{
balance = initialamount;
}
to
GoCardAccount::GoCardAccount(long initialamount, BankAccount * pba) :
balance (initialamount), ba(pba) {}
The argument
BankAccount(ba)
won't store argument passed to ctor to ba, it means that argument passed in function call, which will be placed on stack, will has identifier ba.
You should use different name than member variable
It has to be pointer (in your case)
In member initialize list you have to assign this value to member variable
Example
GoCardAccount::GoCardAccount(long initialamount, BankAccount * pba) : balance (initialamount), ba(pba) {}