Is there a way to count member variable of a class in compile time?

What I want to do is to check member variable count of a class, as some newbie might write too much member variable to read. Is there some way to get it?

We did do code reviews, but a static_assert(GET_MEM_VAR_COUNT(ClassA) < 10) might be more straight and clear.

Solution

Until we get reflection, you are stuck using another tool to check the number of members in a class.

We have a few crude ways to get reflection now, with many limitations. If you only have a data struct, then you can use Boost Fusion to define your class such that you can assert on its size, for example:

#include <string>

#include <boost/fusion/include/define_struct.hpp>
#include "boost/mpl/size.hpp"

BOOST_FUSION_DEFINE_STRUCT(
    (my_namespace), my_class,
    (std::string, member1)
    (int, member2)
    (int, member3)
    (double, member4)
//Uncomment me to trigger assert  (double, member5)
)

static_assert(boost::mpl::size<my_namespace::my_class>::type::value < 5, "Classes must have fewer than 5 members");

Is there a way to count member variable of a class in compile time?

Demo