Class Problem

[RobertEagle]

Hi,

I've just started learning object programming in c++ and I have a problem with my code.

It gives me these errors:

1.error C2065: 'RegistrationForm' : undeclared identifier
2.error C2146: syntax error : missing ';' before identifier 'regForm'
3.error C2065: 'regForm' : undeclared identifier
4.error C2061: syntax error : identifier 'RegistrationForm'
5.error C2065: 'regForm' : undeclared identifier
6.error C2228: left of '.setValue' must have class/struct/union
7. type is ''unknown-type''

My code is:

#include <iostream>
using namespace std;

class sample
{
public:static void main()
	   {
    RegistrationForm regForm = new RegistrationForm();
	regForm.setValue(102,324);
	   }
};

class RegistrationForm
{
    void setValue (int course, int student)
	{
		cout << "Course " << course << " has been dropped from student " << student << endl;
	}
};

Can you help me? I'm standing in front of this situation and for hours I couldn't find an answer.

Thank you,
RobertEagle

[Computergeek01]

Move your definition for the "RegistrationForm" class above your definition for the "sample" class. This should fix the issue.

[RobertEagle]

Ok, I made this change and it gave me the error that my function from RegistrationForm is private so I made it public.

But then it gave me another error. And this is:
1.error C2440: 'initializing' : cannot convert from 'RegistrationForm *' to 'RegistrationForm'. No constructor could take the source type, or constructor overload resolution was ambiguous

Now my code looks like this:

#include <iostream>
using namespace std;

class RegistrationForm
{
public:void setValue (int course, int student)
	{
		cout << "Course " << course << " has been dropped from student " << student << endl;
	}
};

class sample
{
public:static void main()
	   {
    RegistrationForm regForm = new RegistrationForm();
	regForm.setValue(102,324);
	   }
};

[Peter87]

Looks like you are used to Java.

Do you want regForm to be an RegistrationForm object or a pointer to a RegistrationForm object? new is used to dynamically allocate an object. It gives you a pointer to the allocated object. You have to use delete on the pointer to free the memory when you no longer need it.

RegistrationForm* regForm = new RegistrationForm();
regForm->setValue(102,324);
delete regForm;

It doesn't look like you actually need dynamic allocations and pointers here so best avoid it. Just create the object and call the function like this:

RegistrationForm regForm;
regForm.setValue(102,324);

The order in which you declare/define things matter. That's why you should define RegistrationForm before sample.

In C++ the main function should be a free function (not a class member) and have return type int.

[BlackSheep]

public static void main()?
Are you sure you aren't trying to learn C++ using a Java tutorial? Either that or you have a Java background and are trying to apply the same techniques to C++. That won't work.
Your error comes from this line:
RegistrationForm regForm = new RegistrationForm();
In order to use "new" in order to assign memory for the variable, regForm needs to be a pointer, as such:
RegistrationForm *regForm = new RegistrationForm();
I think in your case it's much easier to just declare regForm the way you did, but forget about "new" and pointers for now:
RegistrationForm regForm;
This way you can use regForm just as you would expect. There's no need to explicitly call new in order to create the object. It already exists.
I also suggest you start working your way through the C++ tutorials on this site.

[RobertEagle]

Well, this is what the book told me, and it's a C++/Java/C# book.
Now, really, I'm not used with Java.
I'm used to C++, and maybe this is why I can't really figure out how it does work.

How would it look like in C++?

[BlackSheep]

int main()
{
RegistrationForm reg;
reg.setValue(0,0);
}

EDIT: Don't stick it inside a class. I suggest creating a main.cpp file for your main function.

[Computergeek01]

The only thing that public:static void main() does is declare a member function for the "sample" class called "main" with no return type. Although it may be a little confusing to look at at first, no compiler is going to try to make that the entry point of the application so it's technically not wrong.

[RobertEagle]

Yes, man, another life. I love saying that now it works flawless.
I know quite well C++, I've been using it for a long time making complex mathematics structures, but now I decided to take it to the next level. Through it I won a national contest.

I bought this book called OOP demystified, and I'm at page 20 and it looks "heavy", and sincerely I want to learn c++, because it's simple and straight. Is it a good idea studying this book or should I check the tutorials from this website?

[BlackSheep]

True, but I doubt this is what the OP wanted.

[RobertEagle]

Thank you very much for your help.