Is there a way to use Object.factory with templated classes? Or some way to construct templated classes given RTTI of an instance?

[Steven Schveighoffer]

On 9/26/18 4:41 PM, Chad Joan wrote:
> Hi all,
> 
> I'm implementing a deep-copy method for a tree of templated class 
> instances.  As part of this, I need some way to copy each node. I want 
> to avoid code that does things like casting objects into byte arrays and 
> then copying raw bytes; I want all operations to be memory safe things 
> that I can use at compile-time.  So I planned to make all of these have 
> default constructors and use Object.factory to at least create the 
> correct instance type at the destination.  The classes can implement 
> auxiliary copy methods if they need to copy anything that isn't already 
> handled by their deepCopy method.
> 
> But I ran into a problem: Object.factory doesn't seem to be compatible 
> with templated classes.

Object.factory is a really old poorly supported type of reflection. I 
would not depend on it for anything.

You are better off using your own registration system.

As far as choosing the design for your problem, you can use:

auto obj = typeid(obj).create();

which is going to work better, and doesn't require a linear search 
through all modules/classes like Object.factory.

If it were me, I'd probably instead implement a clone virtual method. 
This way if any custom things need to occur when copying the data, it 
can be handled.

-Steve