Question

I’m a C# programmer trying to muddle through C++ to create a Windows Forms Application.
I have a Windows Form that makes use of a user-created class. Basically I’m trying to use a constructor that takes parameters, but my form won’t let me initialize the object with parameter. Here’s the code, hopefully somebody can explain the problem to me because I’m completely baffled…

Here’s my header file: BankAcct.h

public ref class BankAcct
{
    private:
        int money;

    public:
        BankAcct();
        BankAcct(int);
        void Deposit(int);
        void GetBalance(int&);
};

And my definition file: BankAcct.cpp

#include "StdAfx.h"
#include "BankAcct.h"

BankAcct::BankAcct()
{
    money = 0;  
}
BankAcct::BankAcct(int startAmt)
{
    money = startAmt;
}
void BankAcct::Deposit(int depAmt)
{
    money += depAmt;
}
void BankAcct::GetBalance(int& balance)
{
    balance = money;
}

And finally my main form. Won’t copy the whole thing, of course, but I’m trying to declare the new bank account object, and start it with a balance of say $50.

private:
    BankAcct myAccount(50);    //does not work!  WHY??

//private:
  //BankAcct myAccount;    //works

then in the form constructor my code is this:

public:
    frmBank(void)
    {
        InitializeComponent();
        int bal;
        myAccount.GetBalance(bal);
        lblBankBalance->Text += Convert::ToString(bal);
    }

I’ve included the BankAcct.h file at the top of my frmBank.h, what else am I doing wrong here? It works great if I use the default constructor (the one that starts the bank balance at zero). I get the following error messages:

error C2059: syntax error: ‘constant’

and

error C2228: left of ‘.GetBalance’ must have class/struct/union

Thank you for any and all help on this one!!

Answer 1

C#-style initialization does not work in C++. You need to put initializers in the initialization section of your constructor (i.e. between : and the opening brace { of the constructor:

public:
    MyForm() : myAccount(50) {
        // Your constructor
    }
private:
    BankAcct myAccount;

The way you have it now, myAccount is not defined as BankAcct, so calls of GetBalance do not compile either.