• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
Xeeynamo

Two classes that calls each other

3 posts in this topic

Hi!
I'm trying to compile unsuccessfully a project that has two classes. The class A has class B as a member, and there is a function where send its pointer to class B. I read already a lot of other sites, forum etc an the trick is called Foward Declaration, but seems to not work... Basically the code is this:
[code]
#include <stdio.h>
class A
{
public:
B b;
void Init()
{
printf("Init A\n");
b.Init(this);
}
void Ok()
{
printf("OK A!\n");
b.Ok();
}
};
class B
{
public:
A *a;
void Init(A *param)
{
printf("Init B\n");
a = param;
a->Ok();
}
void Ok()
{
printf("OK B!\n");
}
};

int main()
{
A a;
a.Init();
}
[/code]
0

Share this post


Link to post
Share on other sites
Separate declaration and definition.
[source]
class A;

class B
{
public:
A *a;
void Init(A *param);
void Ok();
};

class A
{
public:
B b;
void Init();
void Ok();
};

void B::Init(A *param)
{
printf("Init B\n");
a = param;
a->Ok();
}

void B::Ok()
{
printf("OK B!\n");
}

void A::Init()
{
printf("Init A\n");
b.Init(this);
}

void A::Ok()
{
printf("OK A!\n");
b.Ok();
}
[/source]
The forward declaration of A is necessary to define the pointer member and parameter in B. The full definition of B is then necessary so that it can be a member of A. Finally, the member functions are defined once all classes are fully defined.
2

Share this post


Link to post
Share on other sites
Oh great! So that was the problem, I need to separate the declarations from definitions. Thank you very much, you was clear about the explaining [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]
0

Share this post


Link to post
Share on other sites
[quote name='Retsu90' timestamp='1328903774' post='4911766']
Oh great! So that was the problem, I need to separate the declarations from definitions. Thank you very much, you was clear about the explaining [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]
[/quote]

To expand, one of the reasons you were probably having issues with forward declaration is because forward declaration only really works for pointer types. So if you were trying to forward declare class B before class A, you'll notice class A creates a full B object, not a pointer to a B object, so forward declaration won't solve the problem for that one. You'll have to fully declare class B before class A.

Now on the other hand, class B uses a pointer to an A object, so forward declaring class A before class B will work. That's why BrotherBob switched the order of class A and class B.

But like BrotherBob said, separating the definitions and the declarations is also necessary here, as he's done.
1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0