Using a template to create arrays of varying length inside of class in C++11

Question

Say I have a class:

template <int S1>
class Cont {
    private:
       std::array<int, S1> nums;
    public:
       Cont(std::array<int, S1> ns);
}

When trying to link my program, I am getting an error saying that, for example, Cont(std::array ns) is undefined. So am I doing something wrong? Or will this never work due to how arrays work?

EDIT: Sorry, I should have mentioned that the constructor is defined. I was only giving the header to illustrate what I meant.

See http://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file — Brian Bi, Feb 24 '16 at 21:45
It might help to _also_ give a) a definition and b) an instantiation, such that all together it is a complete failing example. — davidbak, Feb 24 '16 at 21:47
Looking at what Brian linked I think the problem is that I never instantiated. Once I get back to my desk I will try it out — ragesalmon, Feb 24 '16 at 21:48
@davidbak the problem was that I hadn't instantiated the template. Thanks for the link. — ragesalmon, Feb 24 '16 at 21:57
potential duplicate of http://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file — Guillaume Racicot, Feb 24 '16 at 22:19

score 3 · Answer 1 · answered Feb 24 '16 at 21:37

3

Cont(std::array<int, S1> ns)

Is only a declaration, you need to define it as well.

like:

Cont(std::array<int, S1> ns){
    // code
}

answered Feb 24 '16 at 21:37

Rana

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Using a template to create arrays of varying length inside of class in C++11

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