on Fri Sep 14 2007, Dan Posluns wrote:

Okay, I'm a lot closer to my goal of having an automated factory of objects that are dynamically polymorphic but have their inheritance set up through static means.

What I have now is something like this:

// My factory template template struct Factory { Base *create() { return new Derived(); } };

// My vector of factories for the different Derived types typedef mpl::vector< Factory, Factory, Factory > MyFactories;

(I actually use MPL to automatically cross and combine different classes, which is pretty cool.)

Now I could create a vector of the same length with every type as a pointer to a Factory function, and with Fusion I could probably instantiate it (although I haven't got that working yet). But that still wouldn't get me what I want, which is a table of those factory functions that I can index into at run-time.

Can anyone suggest a technique for doing this?

If you want to index it at runtime and get anything more than a void* back, you need to add dynamic polymorphism somewhere so that you have a common interface through which all these factories can be used. One possibility is to create a FactoryBase class with virtual functions and derive all your Factory templates from it. As long as the factories are all creating the same Base, you should be OK. I would then use fusion to convert the mpl vector into a tuple (so you don't have to dynamically allocate all the Factories) and use fusion::for_each to fill up an array of FactoryBase pointers. HTH, -- Dave Abrahams Boost Consulting http://www.boost-consulting.com The Astoria Seminar ==> http://www.astoriaseminar.com