I can see the technique but frankly I'd have to see some good uses of it before being convinced. Have you put this concept to use (or at least seen it done well)?

I first saw this technique used to handle multiple "look and feels" when drawing widgets. You would ask the factory for a new scrollbar, it would consult a policy object, which would tell it what (available) class to use, and the factory would hand back a new instance of whatever type the policy object said to use.

I've also used a similar technique when building "plugin" mechanisms. At startup, the application reads and initializes a set of plugins, each of which inherits from Plugin. At initialization time, each plugin registers itself with Plugin. Plugin provides factory methods, a query method that hands back the names of all registered plugins, and a mapping of plugin name to plugin instance.

In reply to Re: Re: Re: Re: Constructor/Factory Orthodoxy by dws
in thread Constructor/Factory Orthodoxy by mojotoad

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