• 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
Deek880

initializing a vector c++

8 posts in this topic

I have a game class in which I want to initialize a vector of players: Please note that this has to be a reference: It goes like this:

#define GAME_H
#include "player.h"
#include <vector>
#include <iostream>
#include <iterator>

class game
{

public:

	game();
	~game();

	player P;
	std::vector<player>&gPlayerVec;
	std::vector<player>gPlayerVecCopy;

	void PlayGame();




};
#endif //GAME_H

I get the following error when I compile:

c:\mpgames2\pointer\game.cpp(9) : error C2758: 'gPlayerVec' : must be initialized in constructor base/member initializer list
        c:\mpgames2\pointer\game.h(17) : see declaration of 'gPlayerVec'
c:\mpgames2\pointer\game.cpp(9) : error C2758: 'gPlayerVecCopy' : must be initialized in constructor base/member initializer list
        c:\mpgames2\pointer\game.h(18) : see declaration of 'gPlayerVecCopy'

 

the game constructor is here:

game::game()
{
	

	gPlayerVec.push_back(P);

}

What do I need to put in there to fix this problem

0

Share this post


Link to post
Share on other sites

I may be wrong, but I don't think you can initialise references like that. Is there a vector that it is actually referencing? If so how about putting the line you have for initialising the reference into the argument of the constructor? So you can pass in the reference as you create the game class.

Edited by Godmil
0

Share this post


Link to post
Share on other sites

Although it seems to appear as a variable, you have to think of a reference as an alias for an existing value. (Although a function declaration can have a reference as an argument, the actual reference is constructed from an existing value when the function is actually called.)  Just as "John Doe" can be an alias only if there's a person with another name, a reference must be defined when it's declared.

 

EDIT: Perhaps if you explain what problem you're dealing with, an alternate solution can be suggested.

Edited by Buckeye
0

Share this post


Link to post
Share on other sites


Please note that this has to be a reference:

 

Ok, first question: why? Is it using an object that someone else owns? In which case it absolutely should be a reference (maybe even a const reference, if you're just iterating over the collection). If that is the case, then the compiler is giving you the answer. Your reference must be initialised when the containing object is constructed. The simplest way to do this is to pass vector you want to refer to in the constructor arguments as L.Spiro has demonstrated.

 

If, on the other hand you actually want polymorphic behaviour, you should follow L. Spiros second example, but just be aware of who has the responsibility for the memory (i.e. the ownership semantics).

0

Share this post


Link to post
Share on other sites

I think Spiro answered the question. I haven't tried to implement his code yet, (but thank you for the help spiro) but I think he is exactly right

 

What I'm trying to do this: I have a fixed size array of players in player class, then I have a vector of player waiting to get into the game, gPlayerVec, then the game players are in gPlayerVecCopy that are active, This is a vector with players back inserted from gPlayerVec.

 

When a player sits out he is poped out of the vectors, but the player array keeps track of what would have been his opportunities. When the player comes back in he is pushed back into the vector.

 

The vectors aren't recognizing the changes that have been made to the player when he is put back in. Or lets say when I try to change a variable directly from the underlying player in the player array, the vectors of players aren't picking up on it.

0

Share this post


Link to post
Share on other sites

I think Spiro answered the question. I haven't tried to implement his code yet, (but thank you for the help spiro) but I think he is exactly right

 

What I'm trying to do this: I have a fixed size array of players in player class, then I have a vector of player waiting to get into the game, gPlayerVec, then the game players are in gPlayerVecCopy that are active, This is a vector with players back inserted from gPlayerVec.

 

When a player sits out he is poped out of the vectors, but the player array keeps track of what would have been his opportunities. When the player comes back in he is pushed back into the vector.

 

The vectors aren't recognizing the changes that have been made to the player when he is put back in. Or lets say when I try to change a variable directly from the underlying player in the player array, the vectors of players aren't picking up on it.

 

Because you are using a vector of players when you should be using a vector of pointers or references to players.

 

E.g.  

vector<Player> player_vec;
Player p("someplayer")
p.setFoo(0);
 
player_vec.push_back(p);
p.setFoo(1);
 
Player p2 = player_vec[0];   
p2.getFoo();  /// returns 0
 

This shoudl be somethign like 

vector<Player*> player_vec;
Player p("someplayer")
p.setFoo(0);
 
player_vec.push_back(&p);
p.setFoo(1);
 
Player *p2 = player_vec[0];   
p2->getFoo();  /// returns 1

Edit: Basically what Spiro suggested

0

Share this post


Link to post
Share on other sites

Actually Spiro's method of initializing a reference to a vector didn't compile 10 errors. But I'm using visual c++6.0 which is a 1998 compiler, even though it was current up to 2004.

 

This works, its a mix of both suggestions:

 

game.h

 

std::vector<player *>playervec;

 

player * P

 

game.cpp

 

game::game()

{

     P = new Player;

    gPlayerVec.push_back(P);

}

 

Now, a change  works across all vectors and the underlying player whether initiated from the player or the vector.

 

Question, Is it worth re-writing the whole program which has grown up with a constant array of Players?

I can accomplish the same thing with an I & J loop setting the requisite elements equal to each other at the end of every game run loop.

0

Share this post


Link to post
Share on other sites

I'm using visual c++6.0

 

Stop right there. There have been multiple free versions of Visual C++ since then, all of which are better than 6.0. Here's the latest one.

 

Do your self a favour and get a newer version before you write another line of code. I'm not even slightly kidding. 

Edited by ChaosEngine
2

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