Linking error with methods using class templates

Question

I need to use my class template inside one of the member functions (class methods), as shown below :

Declaration :

template <int N>
class Array
{
private :
    int var[N];
public : 
    void increment ();
};

Definition :

template <int N>
void Array<N> :: increment ()
{
    for (int i = 0; i < N; i++)
    {
        cout << i << endl;
    }
}

Instantiation and method call in Main.cpp:

Array <5>var;

int main()
{
    var.increment();

    system ("pause");
}

I keep getting a linking error saying "1 unresolved externals" in Main.obj (Main.cpp). Please consider all "cout" and "using namespace std" to be already done in the background. I'm just adding the relevant code here.

My main problem is that I don't know how to use the class template parameter (N) inside one of the class's methods.

UPDATE: Sorry I'm late but I've found a solution to this. Thanks for the help all.

It runs in my pc. I putted all in the same file and worked. How are you compiling/linking? — Eduardo Pascual Aseff, Feb 14 '20 at 04:37
@EduardoPascualAseff really? What compiler are you using? I'm on windows MSVC. Maybe they have different implementations? — Tine, Feb 14 '20 at 04:39
You may have run up against [Why can templates only be implemented in the header file?](https://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file) — user4581301, Feb 14 '20 at 04:42
@user4581301 very helpful. Thanks. I'll try it out and update my post if needed. — Tine, Feb 14 '20 at 04:55

score 0 · Accepted Answer · answered Jul 16 '20 at 06:00

0

Just to close this thread because I forgot about it long ago. The problem seems to be the fact that templates can only be implemented in a header file of .tpp file. The link given by @user4581301 helped in clearing this up.

This is the link

answered Jul 16 '20 at 06:00

Tine

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Linking error with methods using class templates

1 Answers1