The most recent time I needed something like this, I wanted to test whether a struct contained a field with a particular name that was convertible to a float (I think float or int16_t in that case). I would have been happy with a test for a field with that name of any type. But I couldn't work out how to do it. Any ideas?
I think below code(incomplete) can test a field with a name of any type. template <int c>struct enable{ typedef void type;}; template <typename T>struct wrapper{ static T value;}; template <typename T, typename E=void>struct has_foo_impl{ enum { value = false };}; template <typename T>struct has_foo_impl<const T, typename enable<sizeof(wrapper<T>::value.foo, 1)>::type>{ enum { value = true };}; template <typename T>struct has_foo : has_foo_impl<const T> {}; struct a{};struct b{ int foo; }; #include <iostream> int main (){ std::cout << has_foo<a>::value << std::endl; std::cout << has_foo<b>::value << std::endl; return 0;}