Michael Marcin <mike.marcin <at> gmail.com> writes:
Joaquin M Lopez Munoz wrote:
OK, please help me make out a more complete picture of the use case you've got in mind. Imagine you have a flyweight type that behaves the way you need/want, let's call it texture_flyweight. The associated key is std::string and the associated value is texture. Now, you write the following:
texture_flyweight fw("wood.texture");
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?
It would go to the factory's construct method which might look like:
void TextureFactory::construct( void* address, const std::string& filename ) { // complex work involving lots of 3rd party libraries // happens here GLuint glTextureName = LoadImage( filename );
// texture stays simple new(address) Texture( glTextureName, filename ); }
This can be covered in a manner similar to the one described in my reply to Scott's post: struct Texture { Texture(GLuint,const std::string&); ... }; struct LoadedTexture:Texture { LoadedTexture(const std::string& filename): Texture(LoadImage(filename),filename) {} }; typedef flyweight<key_value<std::string,LoadedTexture> > TextureFlyweight; Does this address your needs? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo