Yes, I am interested in it. It appears to provide a way to do reflection on a limited basis by using a name to create an object. Hajo Kirchhoff in his LitWindow library also provides a way to do reflection based on names although I do not believe he has the ability which you have to dynamically create objects based on names. The general ideas that you both use, providing a way to register information about types, seems similar. I am interested, more for the ideas involved than for current practical use, in any general mechanism which provides reflection capabilities, where a name can be used to find out type information or variable information at run-time, or where an object can be created based on its name at run-time. The only nit I have to pick is calling your implementation a virtual constructor lib. I do not see where polymorphism comes into play in the actual construction of the objects from its name. Perhaps a "name constructor lib" would be more accurate. Roland Schwarz wrote:
As a byproduct of my current work I factored out a small utility library that implements a virtual constructor.
The implementation is based on boost::any and typeid(...).name(). It features dynamic creation of objects by name (string), and allows for default and custom constructors beeing called.
It could be used as the basic step to object deserialization from a file, creation of operating system dependent implementations, or allow a library to instantiate user-pluggable classes.
The design is inspired by the Io_obj example from Stroustrup's book on C++ programming.
A small example to show the usage:
#include <string> #include <iostream> #include "dynanew.hpp"
using namespace dynanew;
// a simple class hierarchy with abstact base class struct shape { virtual void draw() = 0; };
struct square : public shape { virtual void draw() { std::cout << "I am a square" << std::endl; } };
struct circle : public shape { circle() : radius(0) {} circle(double dr) : radius(dr) {} virtual void draw() { std::cout << "I am a circle of radius: " << radius << std::endl; } double radius; };
// create the type map TYPE_MAP(shape); // square with default constructor TYPE_REGISTER(shape, square); // circle with custom constructor taking a double parameter TYPE_REGISTER1(shape, circle, double); // circle with default constructor TYPE_REGISTER(shape, circle);
int main(int argc, char* argv[]) { std::string type; type = "square"; shape* ps1 = dynamic_new<shape>(type); shape* ps2 = dynamic_new<shape>("circle", 20.0); shape* ps3 = dynamic_new<shape>("circle"); shape* ps4 = dynamic_new<shape>("square", 10.0);
if (ps1) ps1->draw(); // prints: I am a square if (ps2) ps2->draw(); // prints: I am a circle of radius: 20.0 if (ps3) ps3->draw(); // prints: I am a circle of radius: 0.0 if (ps4) ps4->draw(); // does nothing since no ctor available
delete ps1; delete ps2; delete ps3; delete ps4;
return 0; }
regards, Roland
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost