• 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
TheComet

"Forwarding" iterators without losing const?

4 posts in this topic

The title is a little misleading, but I'm not sure what else to call it.

 

Consider the following.

class Bar {};

class Foo
{
public:
    typedef std::vector<Bar*>::iterator iterator;
    iterator begin(){ return m_List.begin(); }
    iterator end(){ return m_List.end(); }
private:
    std::vector<Bar*> m_List;
};

void doStuff( const Foo& foo )
{
    for( Foo::iterator it = foo.begin(); it != foo.end(); ++it ) // ERROR: passing 'const foo' as 'this' argument of 'Foo::iterator Foo::begin()' discards qualifiers
        // do something here with "it"
        ;
}

Changing the function doStuff do the following fixes it, but I'd rather not lose const-ness:

void doStuff( Foo& foo )

What do?

0

Share this post


Link to post
Share on other sites

Thanks! This fixed it:

class Bar {};

class Foo
{
public:
    typedef std::vector<Bar*>::iterator iterator;
    typedef std::vector<Bar*>::const_iterator const_iterator;
    iterator begin(){ return m_List.begin(); }
    iterator end(){ return m_List.end(); }
    const const_iterator begin() const { return m_List.begin(); }
    const const_iterator end() const { return m_List.end(); }
private:
    std::vector<Bar*> m_List;
};

void doStuff( const Foo& foo )
{
    for( Foo::const_iterator it = foo.begin(); it != foo.end(); ++it )
        // do something here with "it"
        ;
}
2

Share this post


Link to post
Share on other sites

Just as a side question but why are you not handling the iteration inside of Foo? You are kind of exposing class internals in this structure you present here and that is generally speaking bad design.

1

Share this post


Link to post
Share on other sites

Just as a side question but why are you not handling the iteration inside of Foo? You are kind of exposing class internals in this structure you present here and that is generally speaking bad design.

Below is all of the relevant code (compressed to the minimum) to do with my question, along with explanations. If there is a more elegant way of handling this, please do let me know (note: may contain typos, as it is not a direct copy of the source code).

 

The project is a Sokoban back-end. If you want to review the entire project, you can do so here: https://github.com/TheComet93/chocobun/tree/master/chocobun-core/core

Be warned though, for I am not that experienced yet, and it may make you face-palm repeatedly.

// container for levels, and basically acts as the interface to the front-end
class Collection
{
public:

    typedef std::vector<Level*>::iterator level_iterator
    typedef std::vector<Level*>::const_iterator const_level_iterator;

    level_iterator level_begin(){ return m_Levels.begin(); }
    level_iterator level_end(){ return m_Levels.end(); }
    const const_level_iterator level_begin() const { return m_Levels.begin(); }
    const const_level_iterator level_end() const{ return m_Levels.end(); }

    // loads all levels from a file and stores them in this collection
    void parse( const std::string& fileName ){
        m_FileName = fileName;
        CollectionParser cp;
        cp.parse( m_FileName, *this );
    }

    // saves all levels in this collection to a file
    void save( const std::string& fileName ){
        CollectionParser cp;
        cp.save( m_CollectionName, *this );
    }
private:

    std::vector<Level*> m_Levels;
    std::string m_FileName;
};

// handles everything to do with level data (tiles), player movement, and so forth
class Level
{
public:
    // stuff do do with the levels
};

// base class for all collection parsers
class CollectionParserBase
{
public:
    virtual void save( std::ofstream& file, const Collection& collection ){}
    virtual void parse( std::ifstream& file, Collection& collection ){}
};

// SOK implementation of a parser
class CollectionParserSOK : public CollectionParserBase
{
public:
    void parse( std::ifstream& file, Collection& collection )
    {
        // parses the file, creates levels using the object "collection" and writes level data to those levels
    }

    void save( std::ofstream& file, const Collection& collection )
    {
        for( Collection::const_level_iterator it = collection.level_begin(); it != collection.level_end(); ++it ) // <---- this is where I need it
        {
            // stream everything to the file (e.g. file << data);
        }
    }
}

// other parser implementations here...

// this is used to save and load collections
class CollectionParser
{
public:
    void parse( const std::string& fileName, Collection& collection ){
        std::ifstream file( fileName.c_str() );
        // check if file is open, etc...

        // determine the file format of fileName here, and create instance of corresponding derived parser
        std::auto_ptr<CollectionParserBase> parser = new // whatever parser was chosen

        parser->parse( file, collection );
    }

    void save( const std::string& fileName, const Collection& collection ){
        // open file, determine format, etc. etc. (see parse method above, it's basically the same)
        parser->save( file, collection );
    }
};

The parser requires access to all Level objects contained within the Collection object, and I found it to be easiest to pass Collection to the parser. In an older version, I passed the level array (std::vector<Level*>) to the parser, but the problem was the parser needed access to various other parts of the Collection object (such as the collection name).

Edited by TheComet
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