Matthijs Möhlmann wrote

Hello all,

I'm currently busy to get things like this working:

struct person { std::string name; int age; };

int main(int argc, char **argv) {

person p; p.name = "Matthijs" p.age = 1234;

std::string key = "name";

// Now try to fetch the value based on the key string. std::cout << p.{key} << std::endl; // does not compile

return 0; }

Of course above doesn't work for obvious reasons.

std::cout << "Name: " << boost::fusion::at_key<keys::name>(x) << std::endl; std::cout << "Age: " << boost::fusion::at_key<keys::age>(x) << std::endl;

Now my question, is there maybe another way to achieve this?

I guess that what you want is a some kind of run-time reflection. int main(int argc, char **argv) { person p; p.name = "Matthijs" p.age = 1234; std::string key = "name"; std::cout << field_at_key(p, key) << std::endl; return 0; } The problem is that we don't know which type person_field_at_key should return. We could type erase the result type and get it lazily when the value is required. The following maps to a field reference template <typename T> field_ref<T> field_at_key(T const& p, std::string const& key) { return field_ref<T>(p,key); } We could overload an apply function specific for field_ref<person> template <typename Visitor> void apply(Visitor& v, field_ref<person> const&p) { if (key=="name") v(p.get_person().name); else if (key=="age") v(p.get_person().age); } The preceding code could be generated by a macro, as it is done STRUCT_ADAPT We could the define a OSTREAM visitor as follows template <typename OSTREAM> struct ostream_visitor { OSTREAM& os_; otream_visitor(OSTREAM& os) : _os(os) template <typename T> operator(T const& v) { os_ << v; } }; template <typename OSTREAM, typename T> OSTREAM& operator<<(OSTREAM& os, field_ref<T> const& p) { ostream_visitor v(std::cout); apply(v,p); return *this; } There are surely some boost related reflection libraries that I don't know that it could be worth looking for as e.g. Boost.Mirror. I don't know if you are looking for this behavior. HTH, Vicente -- View this message in context: http://boost.2283326.n4.nabble.com/Get-fields-from-struct-tp4291964p4292528.... Sent from the Boost - Users mailing list archive at Nabble.com.