Question

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Where to define C++ class member template function and functors that instantiate it?
inclusion of header files in case of templates

I am using class templates. I have several methods in my my class and if I define them in the .cpp file I am getting the linker error

error LNK2019: unresolved external symbol

Do all methods in template classes need to be defined in the header file? It makes my code look yucky but if it’s the only way I am fine with it.

Answer 1

Do all methods in template classes need to be defined in the header file?

Yes. But you can still factor out the parts that don’t rely on template arguments and put those in a regular modules as ordinary functions or as a mixin class:

class NonTemplatedOpsMixin
{
    int bar();  // defined elsewhere
};

template <typename T>
class TemplatedStuff : private NonTemplatedOpsMixin
{
    T foo(T &x) { x += bar(); }
};