David Abrahams wrote: > Alexander Nasonov <[EMAIL PROTECTED]> writes: > >> Well, sometimes it's needed at compile-time. Though, I don't know how >> useful it is. Can you give an example? > > Heh, you caught me! > > Well, if the (member) (function) pointers are available at compile > time they can be inlined away so that using them becomes more > efficient. > > Suppose I want to write serialization code? Can you > serialize/deserialize with a runtime-only framework?
Take a look at my example http://groups.yahoo.com/group/boost/files/describe_classes.tar.gz and its output (formatting added afterwards) <object type="Driver"> <base type="Person"> <member name="gender" type="char">M</member> <member name="birth_date" type="Date"> <member name="year" type="int">1975</member> <member name="month" type="int">12</member> <member name="day" type="int">8</member> </member> <member name="first_name" type="string">Alexander</member> <member name="last_name" type="string">Nasonov</member> </base> <member name="licence_id" type="string">N/A</member> <member name="licence_issue_date" type="Date"> <member name="year" type="int">0</member> <member name="month" type="int">0</member> <member name="day" type="int">0</member> </member> </object> You can see that bases and compound types (like Date) are serialized properly. There is neither pointer nor container support yet. I have some ideas, though. Sone words about how it works. First of all, an address of an object and a type_info are taken. The framework always operates with void* pointer and type_info. Several types (*_nodes) have virtual functions which casts raw pointers back to original type and do some action. For example, class base_node // represent a base of a concrete class { // ... // virtual void* derived_to_base(void* base_ptr) const = 0; }; class member_node // represent a member of a concrete class { // ... // Apply ->* operator to an object pointed to // by raw_ptr and return an address of the result. virtual void* dereference(void* raw_ptr) const = 0; }; The framework uses these functions to access bases or members one by one until it find elemetary types like int, char or std::string. When such type is found you can print it or assign a new value to it. For example, you have a raw pointer to Driver and you want to get a member represended by some member_node node. Let's say node holds a pointer to Driver::licence_issue_date. You can call node.dereference(raw_driver) to get a raw address of this member and node.member_type() to get its type. Then, if member type (Date in this case) isn't an elemenary, repeat the procedure recursively. Otherwise, find a function that can print the member. >> Some other questions. How to map member pointers to names? > > Add a char const* const parameter? Have an additional parallel array > of names? > >> How to find a member? > > By name? By reverse-indexing whatever structure answers the previous > question, of course! At compile time?! I can think of this code but I don't like it so much: template<class Members, const char* Name> struct find_member; template <> struct class_<Driver> // Taken from your post { typedef mpl::vector<Person> bases; static const char licence_id[]; static const char licence_issue_date[]; static const char accelerate[]; typedef mpl::vector< member<int Driver::*, &Driver::licence_id, licence_id> , member<Date Driver::*, &Driver::licence_issue_date, licence_issue_date> , member<void (Driver::*)(), &Driver::accelerate, accelerate> > members; ... }; typedef find_member< class_<Driver>::members, class_<Driver>::licence_id >::type result; -- Alexander Nasonov Remove minus and all between minus and at from my e-mail for timely response _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
