previous definition of a class

[Tourun]

Hey Guys,
In my program I have two classes in two different header files. Each class has a pointer to the other class in it, so when I include the header in each file I get an error stating there's a previous definition of the class. Is there a way around that? Possibly with #ifndef?

[jsmith]

forward declare the classes rather than include the headers.

[Tourun]

Ok, now it's giving me an error for a forward declaration. Here is an example.

user.cpp:6: error: invalid use of incomplete type 'struct Account'
define.h:60: error: forward declaration of 'struct Account'

So what is the difference between needing a forward declaration and needing a header file? I'm self-taught, so forgive me ignorance. :-\

[Hammurabi]

Also remember to use include guards on your headers.

#ifndef _MYHEADER_H_
#define _MYHEADER_H_

class AnotherClass;

class Class {
    AnotherClass* ac;
};
#endif

[Tourun]

Ok, after some research I've found that adding headers into the .cpp files and using forward declarations in the headers is the best way to go. Does that sound right?

[S6k9GNh0]

Header guards should work. If your not sure why they work it's simple: When you define something it's defined in your compiler. If it checks for that defined object again and it's already defined it will not include the remainder of the file.

[Tourun]

I have header guards in all my headers. I never knew why they were necessary but I used them. :-\