Reflex is ROOT's (or actually CINT's) reflection database. It knows everything about all classes, types, and members in the system. We are currently in the process of a major update of Reflex, including changes in the API and its internal structures. Bare with us - you will get proper documentation once this upgrade is finished. Until then this is what you need to know:
Reflex is a container - it does not know anything by itself. You can use genreflex, a python script wrapping GCCXML, or rootcint -reflex or regular rootcint and Cintex, by calling Cintex::Enable(). In the near future, CINT will use Reflex directly; any dictionary loaded by CINT will automatically populate Reflex.
The main user interface to the Reflex data consists of
Note that conversions exist, e.g. ROOT::Reflex::Member is both a scope and a type, thus a ROOT::Reflex::Scope representing ROOT::Reflex::Member can be converted to a ROOT::Reflex::Type. Just check the list of member functions for these types - they are easy to understand.
using ROOT::Reflex; // save typing
Scope s = Scope::ByName("ROOT::Reflex::Scope"); // the scope containing the member we want to query
Member m = s.FunctionMemberByName("SubTypeByName"); // get the function member
Type mt = m.TypeOf(); // we need its type
Type arg = mt.FunctionParameterAt(0); // the type of the first function parameter
cout << arg.Name(SCOPED | QUALIFIED) << endl; // print the scoped and qualified name