[xsd-users] Getting at the autopointers

[James Boyden]

On Wednesday, Nov 16, Boris Kolpackov wrote:

> If I understood you correctly, you want to "detach" some sub-trees from
> the complete document tree and manage them separately. The only way that
> I can think of is by making a copy of the nodes that you are interested
> in (a copy of all the "sub-nodes" will be made automatically). E.g.,
> suppose you have the following schema:
> 
> <complexType name="Foo">
> 
>   ...
> 
> </complexType>
> 
> 
> <complexType name="Bar">
>   <sequence>
>     <element name="foo" type="Foo"/>
> 
>     ...
> 
>   </sequence>
> </complexType>
> 
> 
> Then you can do something like this:
> 
> Bar& b = ...
> 
> auto_ptr<Foo> f (new Foo (b.foo ())); // Make a copy.

Hi,

I admit I haven't yet looked too closely at the XML schema polymorphism
features used to handle things like substitution groups, but if there's
C++ polymorphism involved, wouldn't

	auto_ptr<Foo> f (new Foo (b.foo ())); // Make a copy.

be better expressed as something like

	auto_ptr<Foo> f (b.foo ().clone ()); // Make a clone.

using the "virtual constructor" idiom [1]?


(I note that in the file "schema.hxx" generated by xsd for the
"cxx/tree/polymorphism" example, the classes 'person_type',
'superman_type', 'batman_type' and 'instance_type' all have a function
'_clone', but this function is clearly intended for internal use only,
plus it takes two arguments which I don't understand, so I'm going to
assume that it's not the solution to this problem.)


jb


[1] "virtual constructor" idiom:
 http://www.parashift.com/c++-faq-lite/virtual-functions.html#faq-20.8