Re: Template Class With Static Data Member

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
comp.lang.c++
Date:
Fri, 21 Aug 2009 06:44:24 +0200
Message-ID:
<h6l8nb$plp$1@news.eternal-september.org>
* Immortal Nephi:

Can you create two objects of template class so template class can
have its own copy of static data member instead of shared static data
member?

template< typename T >
class Test
{
public:
    Test() {}
    ~Test() {}

    static T s_data;
};

template< typename T >
T Stack< T >::s_data = 0;


The "Stack<T>::" seems to have escaped from your real code; for the code
presented it should be "Test::".

int main()
{
    Test< long int > a;
    Test< short int > b;

    a.s_data = 1; // OK...Own one copy of static data member
    b.s_data = 2; // OK...Own one copy of static data member

    Test< long int > c;

    c.s_data = 3; // Not OK because static data member is shared by a and
c.

    return 0;
}


You have two options: (A) make s_data non-static, or (B) add at least one more
template parameter.

You do not explain what your goal is, but it seems likely that (A) is the best
choice anyway.

Cheers & hth.,

- Alf

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