ifndef and define statements

My C++ book doesn't give any specific details of how the ifndef and define statements are supposed to be used. If anyone could give a brief summary of how to use them with a base class, a derived class, and a derived class of the derived class.
Ex. Base->Derived->Derived.
This information would be very highly appreciated. Thanks.

It's called an inclusion guard. It simply prevents a class or function from behing defined more than once.

#ifndef NAME
#define NAME

class Name { };

#endif

Do you put just the name of the class you are doing in the statement? EX. #ifndef ACCOUNT_CLASS
#define ACCOUNT_CLASS
class account
{}
#endif
Thanks .

As long as the name is unique, it doesn't matter. If you wish to be proper, naming conventions will use some form of the file or class name using all caps and underscore for spacing.

David

OK. But I have one more question. Suppose I have a base class named account and a derived class named chk_acct, what would be my ifndef and define statements for the derived class? Do I put both the base and the derived within them or just the derived?

Depends on how you code. Typically, to each its own.

David

Let me expand a bit.

You could have both the base and derived class defined within the same header file. In this instance, you could use just one guard if you wanted. Most of the time though, each class will have its own header and source file. In these cases, you will want to separate.

David

I think I understand it. All of my classes have their own header files, so I should just include the name of the header file I am creating in the ifndef and define statements. Is this right?

Typically, yes. If I seem somewhat dodgy in my responses, it is because this topic can really be a matter of style.

But, "typically," for use in a header file you would use the name of the file.

Code:

---

// someheader.h

#ifndef SOME_HEADER_H
#define SOME_HEADER_H

// code

#endif  // SOME_HEADER_H

---

Non-conventional naming can lead to poor readability and reusability. Can you imagine trying to maintain code that followed this kind of logic?

Code:

---

// someheader.h

#ifndef I_LIKE_PICKLES
#define I_LIKE_PICKLES

// code

#endif  // I_LIKE_PICKLES

---

:D
David

Ok. So this really doesn't cause the inheritance to transfer to the derived from the base class. It just checks to see if it has been defined. Right?

The inheritance transfer is guarenteed when you inherit ;).

class A { };
class B: public A { }; // B is guarenteed to have inherited A.

Is that the way it is supposed to be defined in the derived?
Such as:
class account {}
class sav_acct:public account {} ?
The way I was starting the class was going straight to the
class sav_acct:public account with no brackets
If you don't mind, please give me the exact start into the sav_acct class I have specified. I didn't include the ; at the end, but if it needs to be there, please tell me. Thanks for your wisdom of the C++ language.

Viewing my post, I take it I get a happy face for the : followed directly by a p. Sorry bout that

The placement of the bracket doesn't matter.

class A { };

and

class A
{

};

are the same thing.

// account.h

#ifndef ACCOUNT_H_
#define ACCOUNT_H_

class accout {
// body
};

#endif // ifndef ACCOUNT_H_

// sav_acct.h

#ifndef SAV_ACCT_H_
#define SAV_ACCT_H_

#include "account.h"

class sav_acct: public account {
// body
};

#endif // ifndef SAV_ACCT_H_

Thanks a lot. That clears all of it up.