Re: [boost] [flyweight] key value with objects not constructible from a key

Subject: Re: [boost] [flyweight] key value with objects not constructible from a key
From: joaquin_at_[hidden]
Date: 2008-11-12 08:54:31

Michael Marcin escribió:
> The flyweight factory concept seems to be missing a key part of the GoF
> Flyweight pattern's FlyweightFactory participant. The GoF factory
> supplies the flyweight if one exists. This is what the current boost
> flyweight Factory concept does. If no flyweight exists the GoF flyweight
> factory creates one. In the boost flyweight library this functionality
> is somewhere else that doesn't seem to be described in the documentation.
>
> The name factory for what is currently in place is misleading. Isn't it
> really just an associative container?
>   

Well, this terminology issue has been raised before and I finally 
decided to stick with "factory"
for lack of a more descriptive name. It is not an associative container, 
though in most cases
factories are built on top of associative containers. I hope the 
important thing is that the reader
gets a clear understanding of what these factories do in the context of 
Boost.Flyweight.

> I'm trying to use flyweight to represent texture objects right now.
> These are surely a good candidate for use with flyweight as they are one
> of the examples given. My textures are fairly simple objects, with low
> coupling. Creating a texture is however expensive and has a lot of
> dependencies (libjpeg,libpng,etc). I typically have a TextureFactory
> which decouples the construction of a texture from the actual texture
> object and allows the work required to setup the various libraries to
> read images to be reused by all textures constructed from the same
> TextureFactory instance.
>
> It doesn't seem possible to have this decoupling with flyweight.
> Am I missing something?
>   

Not sure if this is what you're after, but have you consulted the 
section on key-value
flyweights?

http://svn.boost.org/svn/boost/sandbox/flyweight/libs/flyweight/doc/tutorial/key_value.html

Does this approach your use case?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo