// find all foreign keys fields typedef mpl::filter_view<table, is_same<mpl::back<mpl::_>, tags::foreign> >::type iter_2; ^^^^^^ not needed
Why are you calling this type sequence "iter_2"? It's not an iterator, is it?
Sorry this was my error. But how can I use the filter_view result to do something useful? For what I understand the filter_view results in a lazy forward sequence and though, why not use it with the transform1 algorithm. The following code displays what I trying to do. #include "boost/mpl/vector.hpp" #include "boost/mpl/list.hpp" #include <boost/mpl/find_if.hpp> #include <boost/mpl/at.hpp> #include <boost/mpl/filter_view.hpp> #include <boost/mpl/transform.hpp> using namespace std; using namespace boost; namespace fields { struct id { void print() { cout << "id" << endl; } }; struct name { void print() { cout << "name" << endl;} }; struct address { void print() { cout << "address" << endl; }}; struct birthday { void print() { cout << "birthday" << endl; }}; } namespace tags { struct primary {}; struct foreign {}; struct no_key {}; } typedef mpl::vector<fields::id , tags::primary> id_field_t; typedef mpl::vector<fields::name , tags::foreign> name_field_t; typedef mpl::vector<fields::address , tags::foreign> address_field_t; typedef mpl::vector<fields::birthday, tags::no_key> birthday_field_t; typedef mpl::vector< id_field_t , name_field_t , address_field_t , birthday_field_t > table; // finds primary key field typedef mpl::find_if< table, is_same< mpl::at< mpl::_1, mpl::int_<1>
, tags::primary > >::type primary_key_t;
template <typename T> struct add_vector { typedef mpl::at_c< T, 0 >::type field_t; typedef std::vector<field_t> type; }; // find all foreign keys fields typedef mpl::filter_view<table, is_same<mpl::back<mpl::_>, tags::foreign> > foreign_keys_view_t; typedef mpl::transform1< foreign_keys_view_t, add_vector<mpl::_1>
::type foreign_key_vectors_t;
int _tmain(int argc, _TCHAR* argv[]) { return 0; } Regards, Christian