• 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
Chris_J_H

Help with Polymorphic Class Design

6 posts in this topic

Hi - apologies if this is a bit vague but I am trying to understand the consequences of some base class design choices in my game engine. Below are 2 simplified Process classes that are designed to be used as Base Classes. It seems to me on the face of it Process1 is a better design choice as it demands way less of clients' derived classes - eg, having to remember to invoke Process1::VPause() - although I guess there is a loss of flexibility... In Derived2 for example the client could choose not to pause the process if some condition is met.
 
Insight/Advice appreciated - is there a better way? I really hate the routine requirement to invoke the base class VPause()... it seems to be asking for trouble.

 

[source lang="cpp"]
class Process1
{
public:
    virtual ~Process1();
 
    bool GetPaused() const {return m_bPaused;}
    void SetPause(bool b) {if (b!=GetPaused()) {m_bPaused = b; VPause(b);}}
 
protected:
    virtual void VPause(bool b) { }
 
private:
    bool m_bPaused;
};
 
class Derived1 : public Process1
{
//...
   void VPause(bool b) override { /* do something - no need to worry about m_bPaused, invoking Process1::VPause() etc*/}
};
 
// --------------------------------------------------------------------------------
 
class Process2
{
public:
   virtual ~Process2();
 
   bool GetPaused() const {return m_bPaused;}
   virtual void VPause(bool b) {m_bPaused = b;}
 
private:
   bool m_bPaused;
};
 
class Derived2 : public Process2
{
//...
   void VPause(bool b) override {
   if (b!=GetPaused()) {
      //...
   }
   Process2::VPause(b);}
};

[/source]

 

0

Share this post


Link to post
Share on other sites

I believe this is relevant: http://www.gotw.ca/publications/mill18.htm

Good link! Gets right to the heart of the matter.... I've been taking examples for game system designs from Game Coding Complete which mostly uses Public Virtual Interface methodology and have suffered with the complexity of my derived classes. The alternative is much kinder on the smaller-brained.

0

Share this post


Link to post
Share on other sites

Hmmm, I would say that the Process object itself shouldn't be maintaining the paused state. The process doesn't care whether or not it's paused, it just cares whether or not its update method is called.

 

Rather the 'paused' status of the application is managed by some higher level state of the application. For example, taking a game-engine approach, you would generally have a GameState system.

 

Given two game states "Active" and "Paused", the active state calls the processes update method and the paused state doesn't. This can be extended to other process management styles also ofcourse.

 

I just don't think 'paused' is a state that belongs to the process itself and should be externally managed by the application.

 

n!

Edited by nfactorial
0

Share this post


Link to post
Share on other sites

Hmmm, I would say that the Process object itself shouldn't be maintaining the paused state. The process doesn't care whether or not it's paused, it just cares whether or not its update method is called.

 

Rather the 'paused' status of the application is managed by some higher level state of the application. For example, taking a game-engine approach, you would generally have a GameState system.

 

Given two game states "Active" and "Paused", the active state calls the processes update method and the paused state doesn't. This can be extended to other process management styles also ofcourse.

 

I just don't think 'paused' is a state that belongs to the process itself and should be externally managed by the application.

 

n!

nfactorial - yes, I think you are right if the Process doesn't need to be paused independently (which I guess mostly it doesn't....) - it can also get more complicated in some processes such as Sound Processes whereby actions must be performed entering and exiting the paused state...- however, this was just a simple example to illustrate the general concern of mixing implementation detail and interface in the same virtual functions.

0

Share this post


Link to post
Share on other sites

 Ahh, I guess I miissed what you were asking sorry. In the example I would usually call the VPause method something more like OnPause or OnPauseChanged though it's all a matter of opinion there smile.png I think the name VPause threw me as I wasn't sure what the V was for.

 

I generally can take either approach, depending on the situation.  I would usually base the choice on whether it is valid for the base implementation to be skipped ie. if you allow someone to overriide the function then you are stating that "if you don't want the default behaviour, don't call the base class". If the base functionality is not optional (ie. the base class implementation must be performed regardless of what a derived class wants to do) then I would do what your first example does.

 

n!

Edited by nfactorial
1

Share this post


Link to post
Share on other sites

 Ahh, I guess I miissed what you were asking sorry. In the example I would usually call the VPause method something more like OnPause or OnPauseChanged though it's all a matter of opinion there smile.png I think the name VPause threw me as I wasn't sure what the V was for.

 

I generally can take either approach, depending on the situation.  I would usually base the choice on whether it is valid for the base implementation to be skipped ie. if you allow someone to overriide the function then you are stating that "if you don't want the default behaviour, don't call the base class". If the base functionality is not optional (ie. the base class implementation must be performed regardless of what a derived class wants to do) then I would do what your first example does.

 

n!

Thanks - that makes sense.

0

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