Scott McMurray <me22.ca+boost <at> gmail.com> writes:
On Wed, Nov 12, 2008 at 16:09, Joaquin M Lopez Munoz <joaquin <at> tid.es> wrote:
If an equivalent flyweight already exists then there is no problem, fw will be assigned the same texture object, this is how Boost.Flyweight currently works. Now, imagine that no equivalent texture exists, and yet you can't construct a texture object from "wood.texture" alone. How would you have then the above statement behave?
Perhaps there is no constructor for a texture that takes the key, but instead there's some load_texture function that can construct a texture from the key?
Then you can do something like this: struct texture { ... }; texture load_from_texture(const std::string) { ... } struct loaded_texture:texture { loaded_texture(const std::string& str): texture(load_from_texture(str)) {} }; typedef flyweight<key_value<std::string,loaded_texture> > texture_flyweight; Note that loaded_texture can be treated as an implementation artifact: texture_flyweight is convertible to texture, which is the type you're interested about. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo