Thread: Class not declared in the scope

Hi,

I'm running into trouble here as I'm programming C++ with QT4.3.

Here's a snippet

Code:

#Asteroid.h
#ifndef ASTEROID_H
#define ASTEROID_H
#include <QPainter>
#include "AsteroidList.h"

class Asteroid
{

  public:
    Asteroid() { AsteroidList list; }
    void addAsteroid(int,int,int);
    void displayAsteroid();
    void draw(QPainter&);
};
#endif

Code:

#AsteroidList.h
#ifdef ASTEROIDLIST_H
#define ASTEROIDLIST_H

#include <QPainter>
#include "AsteroidNode.h"

class AsteroidList
{
   public:
     AsteroidList();
     Asteroid* first;
     void addAsteroid(int,int,int);
     void drawAsteroid(QPainter&);
     void display();
   private:
     AsteroidNode* a_first;
};
#endif

Code:

#AsteroidList.cpp
#include "AsteroidList.h"
#include <iostream>

//Default Constructor
AsteroidList::AsteroidList()
  {
    a_first = NULL;
  }

As I compile with QT4.3, I encountered this error
Asteroid.h: In constructor ‘Asteroid::Asteroid()’:
Asteroid.h:15: error: ‘AsteroidList’ was not declared in this scope
Asteroid.h:15: error: expected `;' before ‘list’
Asteroid.cpp: In member function ‘void Asteroid::addAsteroid(int, int, int)’:
Asteroid.cpp:13: error: ‘list’ was not declared in this scope
Asteroid.cpp: In member function ‘void Asteroid::displayAsteroid()’:
Asteroid.cpp:19: error: ‘list’ was not declared in this scope
Asteroid.cpp: In member function ‘void Asteroid::draw(QPainter&)’:
Asteroid.cpp:25: error: ‘list’ was not declared in this scope

What i'm concerned is, why is the AsteroidList class not detected in Asteroid.h file even if I've included them?

Please help.

P.S. The codes are incomplete as I'm focusing only on why the class name is not there.

>> #AsteroidList.h
I hope that's not actually in your file. If you want to have the name of the file in the file, use:

Code:

// AsteroidList.h

>> #ifdef ASTEROIDLIST_H
That should be #ifndef, not #ifdef. I think this is causing your first error (and probably others).

You are going to need a forward declaration for Asteroid in your AsteroidList.h file. Put this just below the includes:

Code:

class Asteroid;

Originally Posted by Daved

>>
You are going to need a forward declaration for Asteroid in your AsteroidList.h file. Put this just below the includes:

Code:

class Asteroid;

In addition to that you will have to change the constructor of Asteroid to take either a pointer or a reference to an AsteroidList.

Originally Posted by DarrenY

What i'm concerned is, why is the AsteroidList class not detected in Asteroid.h file even if I've included them?

That is because when including AsteoidList.h, AsteroidList.h includes Asteroid.h but then ASTEROIDLIST_H is already defined and AsteroidList.h will not be read anymore -> class AstreoidList is undefined for class Asteroid.

Kurt

>> In addition to that you will have to change the constructor of Asteroid to take either a pointer or a reference to an AsteroidList.

I don't think that's necessary. Asteroid can know about AsteroidList and include the definition of that class as long as AsteroidList only requires a forward declaration of Asteroid and doesn't need to include its full definition.

Originally Posted by Daved

>> In addition to that you will have to change the constructor of Asteroid to take either a pointer or a reference to an AsteroidList.

I don't think that's necessary. Asteroid can know about AsteroidList and include the definition of that class as long as AsteroidList only requires a forward declaration of Asteroid and doesn't need to include its full definition.

Yes. Shure.
My excuse is just that I read this

Code:

    Asteroid() { AsteroidList list; }

as a constructor that takes an AsteroidList as parameter (should have noticed that it makes little sense to pass a list by value ) and then got it all wrong.
Next time I'll activate brains before posting.
Kurt

>> I read this as a constructor that takes an AsteroidList as parameter

Oops. I actually read it the same way both times I looked at it, too.