Many thanks for the reply. However, I can't say this quite adds up for me.
Here's a bit more info on the problem, and what I *think* you were
suggesting.
Any comments greatly appreciated.
What I want to do is:
DOM_NodeList children = node.getChildList();
for (int i=0; i<children.getLength(); ++i)
{
DOM_Node child = children.item(i);
if (child.getNodeType() == DOM_Node::ELEMENT_NODE)
{
DOM_Element element = castNodeToElement(child); // castNodeToElement
how???
DOM_String s = element.getAttribute("attrName");
.....
}
}
Now we have (roughly) the following type structure:
DOM_Element : public DOM_Node // smart-pointers
ElementImpl : public NodeImpl // real nodes
I can see that the following is valid (except for field access
restrictions), because the node.fImpl is really an ElementImpl, even though
node's fImpl pointer is typed as NodeImpl.
DOM_Element element;
element.fImpl = dynamic_cast<ElementImpl*> node.fImpl; // can't do this
due to fImpl being nonpublic
However, the "child" Node object I have is *really* a DOM_Node, *not* a
DOM_Element being accessed by pointer-to-base-class. Therefore, it is *not*
valid to cast this object.
The following code (which I think is what you are suggesting) is valid only
as long as a DOM_Element happens to have exactly the same bytewise memory
layout as a DOM_Node. While this will in fact currently be the case, it is
not guarunteed to be so (eg what if DOM_Element gets an extra member field
in future..)
DOM_Element element = *(reinterpret_cast<Element_Impl*> &child);
Regards,
Simon Kitching
> -----Original Message-----
> From: [EMAIL PROTECTED] [SMTP:[EMAIL PROTECTED]
> Sent: Wednesday, January 05, 2000 2:07 AM
> To: [EMAIL PROTECTED]
> Subject: Re: comments on Xerces-c for HP-UX 10.20 pa-risc2.0
> (HP9000/800)
>
>
>
>
> >Now for the request:
> >I can't figure how to "cast" up the "hierarchy".
> >In particular, I have a DOM_Node, which is of type ELEMENT_NODE. How do I
> >build a DOM_Element referring to the same node??
> >Yes, I can use the DOM_Node methods, but would prefer to cast it and then
> >use the more convenient DOM_Element methods..
> >Presumably I'm missing something very simple...
> >
>
> It works in a Javaesque sort of way, via references.
>
> So its something like:
>
> DOM_Element asElem = (DOM_Element&)domNode;
>
> So you have a target element, which is by value because the DOM node types
> are really just reference counted smart pointers that are always treated
> by
> value, and you cast the node to it by casting it as a reference to a
> DOM_Element type. I believe this is correct, though I always have to
> re-remember this when someone asks.
>
> ----------------------------------------
> Dean Roddey
> Software Weenie
> IBM Center for Java Technology - Silicon Valley
> [EMAIL PROTECTED]
>
