• 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
BaneTrapper

Little help with code, requiring knowledge.

5 posts in this topic

Hello.

I have a base class that has a variable that needs to be set when the class object is made.

But when i inherit the class, i have no idea how to invoke the constructor, what are workarounds?

How can constructor of MainMenu class also invoke Collision constructor?

//I have class like this, its used as a base class
//NOTE its constructor is taking a argument
class Collision

{

public:

    Collision(sf::RenderWindow *RenWin);

    bool Col_RectMouse(sf::RectangleShape &rec);

private:

    sf::RenderWindow *renWin;

};
 
//The functions the above class uses
Collision::Collision(sf::RenderWindow *RenWin)

{

    this->renWin = RenWin;

}



bool Collision::Col_RectMouse(sf::RectangleShape &rec)

{

    int x = sf::Mouse::getPosition(*renWin).x;

    int y = sf::Mouse::getPosition(*renWin).y;

    if(x > rec.getPosition().x &&

       x < rec.getPosition().x + rec.getSize().x &&

       y > rec.getPosition().y &&

       y < rec.getPosition().y + rec.getSize().y)

    {

        return true;//Collision

    }

    return false;//No collision

}
 
//Then a class that inherits the base class
class MainMenu : public Collision

{

public:

    MainMenu();

    void Draw(sf::RenderWindow &renWin);

private:

    sf::RectangleShape Continue, NewGame, Options, Exit;

};
 
//Code of functions for above class
MainMenu::MainMenu()

{ //Error, no default constructor exists for class "Collision"

    Continue.setFillColor(sf::Color(100,100,100));

    Continue.setPosition(0, 0);

//...

}
0

Share this post


Link to post
Share on other sites

MainMenu::MainMenu(sf::RenderWindow* rw) : Collision(rw)


 

I suggest you to study constructor initializer lists.

These two things, thanks!

0

Share this post


Link to post
Share on other sites

The only way to call a constructor of a base class in C++ is through an intialiser list as shown before, this is the same principle as base or super in java. However they work completely opposite from each other. As C# constructs the derived class first and then the base, in C++ however the base gets constructed before the derived class. This is also the reason why you can't call overloaded or virtual methods in the constructor of a C++ class but can in C# and have them being redirected to the derived implementation of that method.

Edited by NightCreature83
1

Share this post


Link to post
Share on other sites

However they work completely opposite from each other. As C# constructs the derived class first and then the base, in C++ however the base gets constructed before the derived class.

This is almost true, but there's one important detail to be aware of. Although objects do indeed start out as the most derived type, with the method table being for the most derived type, the constructors are still run in order from the base class to the most derived class. This is the most sensible order, since a constructor in a base class must be run before the constructor of any derived class in order for the object to be in a consistent state. Therefore, in C# one has to be extra careful when making virtual method calls in a constructor. If the type is not the most derived type in its inheritance hierarchy, the method will be called on a class whose constructor has not yet been run. (See Stack Overflow) Edited by kloffy
1

Share this post


Link to post
Share on other sites

Hello.

I have a base class that has a variable that needs to be set when the class object is made.

But when i inherit the class, i have no idea how to invoke the constructor, what are workarounds?

How can constructor of MainMenu class also invoke Collision constructor?

You probably need to get more familiar with C++, since constructor-call order is a basic concept.

 

But, in short, a class will automatically call the default constructor of its base class before it executes its own constructor.  If you provide a constructor, but it is not a default constructor because it requires an input parameter, then any inherited class's constructor has to explicitly call a base class constructor in its initializer list.  So your options are to either do that and call that constructor, or just provide a default one that takes no parameters.

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