Question

I have a project using cocos2d-x library that contains a lot of classes. I have a .h file contains a global vector. I want to initialize it when the program starts in an intro page class. Intro page class has a graphical surface and a loader. Then I want to use that vector in my main class. The global vector’s code is like bellow:

//globals.h
#ifndef _GLOBAL_H
#define _GLOBAL_H
#include <vector>

vector<int> a;
#endif

I am using push_back in intro page class. I have used extern and static keywords. my program makes a runtime linker error and it say your vector have been declared in appDelegate class (base class of cocos2d). when I put a static keyword behind it, it don’t give me that linker error but it don’t work correctly.
how can I correct this error? if you have another idea instead of this one, please share it. thank you.

Answer 1

You should have a design like the following:

shared.cpp

vector<int> a;

shared.h

extern vector<int> a;

somewhere.cpp

#include "shared.h"
void code() {
  a.push_back(10);
}

Mind that, since you are using C++, you can uses classes as namespaces to avoid cluttering the global namespace, eg:

shared.cpp

vector<int> Common::a;

shared.h

class Common {
  public:
    static vector<int> a;
}

somewhere.cpp

#include "shared.h"
void code() {
  Common::a.push_back(10);
}