CODEWITHSUNDEEP
c++class
krej
krej

Reputation: 468

I keep getting an error saying my class does not name a type

I have one class, called A, and it has it's own header file. Then I have another class, called B, which also has it's own header file. They each have their own .cpp file where I implement all of their functions.

I'm trying to have class B have a variable of class type A as a private variable, but I keep getting the error 'A' does not name a type

My code looks like this:

main.h:

#ifndef MAIN_H
#define MAIN_H

#include "A.h"
#include "B.h"

#endif

main.cpp:

#include "main.h"

int main( int argc, char* args[]) {
  B test;
}

A.h:

#ifndef A_H
#define A_H

#include "main.h"

class A {
  public:
    //public functions
  private:
    //private variables
};
#endif

B.h:

#ifndef B_H
#define B_H

#include "main.h"

class B {
  public:
    //public functions...
  private:
    A temp;
}
#endif

So all of my includes are in main.h, which includes A before B. B has a variable of type A, but it is included from being in main.h and B.h includes main.h. However, I keep getting an error saying:

error: 'A' does not name a type.

I've done some googling, and it seems like that means that A isn't defined when you use it, but it should be defined there since it's being included in main.h, right?

Upvotes: 0

Views: 4597

Answers (3)

sbi
sbi

Reputation: 224069

The problem is that A.h includes main.h, which includes B.h, which tries to use A.

The good way to organize your files would be this:

main.h:

// not needed

main.cpp:

#include "B.h" // for using class B

int main( int argc, char* args[]) {
  B test;
}

A.h:

#ifndef A_H
#define A_H

// no includes needed ATM

class A {
  //...
};
#endif

B.h:

#ifndef B_H
#define B_H

#include "A.h" // for using class A

class B {
  //public functions...
}
#endif

That way, B.h is self-contained and can be used without having to include anything else before it. That's very important as soon as your project grows above the toy level it is at now. Why would anyone trying to use what header x.h provides need to know to also include f.h, m.h, and u.h?

Upvotes: 8

Rémi
Rémi

Reputation: 3745

The code you provide compiles properly if you add a ; at the end of B.h

A better way of doing it would be #include "A.h" in "B.h", instead of #include "main.h"

But it is probably unrelated to your problem.

That kind of error may also be confusing if you are using templates and forget "typename".

Upvotes: 2

Mark Ransom
Mark Ransom

Reputation: 308186

A.h includes Main.h at the top.

Main.h skips A.h because A_H is already defined, then includes B.h.

B.h tries to make use of A, but A.h hasn't finished compiling yet so the type isn't defined.

Upvotes: 0

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