I've been learning the concept of SFINAE in C++ recentlly and I am currentlly trying to use it in a project.
The thing is, what I'm trying to do is different than anything I could find, and I can't figure out how to do it.
Let's say I have a template class called MyParent:
template <typename Elem>
class MyParent;
And a non-template class called MyClass, that inherites it, using char as Elem:
class MyClass : public MyParent<char>;
Now, I want to use SFINAE in order to check if a typename inherites MyParent, regardless of what Elem type is used.
I can't use std::is_base_of, because of the parent's template.
I've tried to do the following:
template <typename T>
struct is_my_parent : std::false_type {};
template <typename Elem>
struct is_my_parent<MyParent<Elem>> : std::true_type {};
Now, if I check for is_my_parent<MyParent<Elem>>::value, it gives me true. Which is good.
However, when I check for is_my_parent<MyClass>::value, I recive false. Which kind of makes sence because MyClass isn't actually MyParent<Elem>, but I didn't manage to get what I wanted.
Is there any convenient way to achive such a thing in C++, other than defining is_my_parent for each and every class that inherites from MyParent?
You might do
template <typename T>
std::true_type is_my_parent_impl(const MyParent<T>*);
std::false_type is_my_parent_impl(const void*);
template <typename T>
using is_my_parent = decltype(is_my_parent_impl(std::declval<T*>()));