C++: declaring an extern vector container in header file causes errors

Question

I tried searching for solution but couldn't find.

So I have a header file items.h:

#ifndef ITEMS_H
#define ITEMS_H

#include <vector>

using std::vector;

int create_item();


class itemClass
{

public:

    short int xTile;
    short int yTile;

    bool playerHas;

    short int category;
    short int weaponCategory;


}extern vector<itemClass> items;


#endif

and then I have items.cpp where I try to use this vector in create_item():

#include "stdafx.h"
#include "SDL.h"
#include "items.h"
#include <vector>

using namespace std;


vector<itemClass> items;

int index = 0;

int create_item()
{
    //select category for the created item
    short int itemCategory = rand() % 3;

    switch(itemCategory)
    {
    case WEAPON:

        //increase weapons list by one
        items.resize(items.size() + 1);

        index = items.size();

        //set appropriate item category
        items.at(index).category = itemCategory;

        items.at(index).weaponCategory = rand() % 9;

        break;

     }

I left out some non-important parts out. Anyway this code works fine as long as I don't declare the vector as extern in the header, but just keep it local. Why does it cause errors when I try to do this?

EDIT: Sorry, I forgot to include errors:

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(12): error C2371: 'items' : redefinition; different basic types

1>
c:\users\aske\documents\c++\roguelike\roguelike\items.h(53) : see declaration of 'items'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(36): error C2228: left of '.resize' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(36): error C2228: left of '.size' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(38): error C2228: left of '.size' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(41): error C2228: left of '.at' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(41): error C2228: left of '.category' must have class/struct/union

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(43): error C2228: left of '.at' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(43): error C2228: left of '.weaponCategory' must have class/struct/union

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(46): error C2228: left of '.at' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(46): error C2228: left of '.weaponCategory' must have class/struct/union

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(47): error C2228: left of '.at' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(47): error C2228: left of '.weaponCategory' must have class/struct/union

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(48): error C2228: left of '.at' must have class/struct/union

1> type is 'int'

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(48): error C2228: left of '.weaponCategory' must have class/struct/union

1>c:\users\aske\documents\c++\roguelike\roguelike\items.cpp(50): error C2228: left of '.at' must have class/struct/union

Put a semicolon before `extern`, as in `};extern vector items;` — Kerrek SB, Jul 23 '12 at 13:57

score 1 · Answer 1 · edited Aug 01 '13 at 13:04

1

You need a ; before extern in the items.h file, then it should compile - but you really don't need to define the items vector in the .h file.

edited Aug 01 '13 at 13:04

Rohit Vipin Mathews

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answered Jul 23 '12 at 14:07

user993833

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C++: declaring an extern vector container in header file causes errors

1 Answers1