Instantiation of template member function

Question

In Class.h:

class Class {
public:
    template <typename T> void function(T value);
};

In Class.cpp:

template<typename T> void Class::function(T value) {
    // do sth
}

In main.cpp:

#include "Class.h"

int main(int argc, char ** argv) {
    Class a;
    a.function(1);
    return 0;
}

I get a linked error because Class.cpp never instantiate void Class::function<int>(T). You can explicitly instantiate a template class with :

template class std::vector<int>;

How do you explicitly instantiate a template member of a non-template class ?

Thanks,

I was asking the question in the context this blog post concerning boost's serialization library : http://www.timoch.com/blog/2013/04/boost-serialization-coupling-issue/ — TiMoch, Apr 12 '13 at 16:02

Andy Prowl · Accepted Answer · 2013-04-12T14:55:48.367

76

You can use the following syntax in Class.cpp:

template void Class::function(int);

The template argument can be omitted because of type deduction, which works for function templates. Thus, the above is equivalent to the following, just more concise:

template void Class::function<int>(int);

Notice, that it is not necessary to specify the names of the function parameters - they are not part of a function's (or function template's) signature.

edited Apr 12 '13 at 14:55

answered Apr 12 '13 at 14:36

Andy Prowl

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what if Class is also templated? – xaxxon Jul 29 '16 at 11:59
I might have figured it out: template void B::do_something(); https://godbolt.org/g/IhMwqM – xaxxon Jul 29 '16 at 12:06

score 6 · Answer 2 · edited Nov 13 '17 at 13:50

6

Have you tried with the following in Class.cpp?

template void Class::function<int>(int value);

edited Nov 13 '17 at 13:50

JFMR

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answered Apr 12 '13 at 14:37

Didier Trosset

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Instantiation of template member function

2 Answers2

Linked

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