How to retain value of static variable inside a same class which has 2 implementations

Question

I have to call a static functions inside a class(say UserApp) which returns static value. Class Definition and declaration done in 2 files.

File1.h:

userApp(){

    static int* foo;
}

file1.cpp:

{
    int* userApp::foo = 0;
    ...
    .
    .

    foo = somevar;

}

The same class(userApp) is implemented in file2 and to avoid linkage error I'm forced to declare and define the static variable in file2 as well.

In file 2.cpp as userApp::foo is initialized to 0 , the return value of function getFoo is always zero.

I need the value associated to foo in file1. Is there any way I can avoid defining static variable in file2? Thanks in advance.

Kahler · Accepted Answer · 2014-04-03 15:18:19Z

0

What a mess :D

If I understood you right, I believe you have to declare the static member as extern in one of the files, to indicate it's actually referencing to a variable declared elsewhere.

answered Apr 3, 2014 at 15:18

Kahler

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4 Comments

Madhu Over a year ago

Two files has declaration and implementation of same class[with some variations in functionalities].Thus the static member variables and functions are to be defined in both r8?

Kahler Over a year ago

Aw, now wait... You are defining the same class in a different way in each file and including both files?

Kahler Over a year ago

That won't work because then it's impossible to tell to which foo you are referring. Give a different name to each class and decide when you want class1::foo or class2::foo. If you want them both to be the same, again, make two different classes and make one of them's foo refer to the other one's foo.

Kahler Over a year ago

If you define a class twice, when you call class::foo, how to know which implementation are you calling?

Community · Accepted Answer · 2017-05-23 11:57:07Z

0

In UserApp.h:

class UserApp {
private:
    static int* foo_;
public:
    static int* getFoo() { return foo_; }
};

In UserApp.cpp:

#include "UserApp.h"

int* UserApp::foo_ = NULL;

In any other where you need to use it:

#include "UserApp.h"
...
int* foo = UserApp::getFoo();

You haven't provided any details about your namespace / class full of static things, but consider making more OO design or in case it seems reasonable to keep it in one class, consider implementing a singleton that would also allow you to hold the information about its state in more reasonable way. (you might end up with something like this)

edited May 23, 2017 at 11:57

CommunityBot

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answered Apr 3, 2014 at 15:18

LihO

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