Re: [xml] xmlAddChild & xmlCopyNode - namespace lost

[Daniel Veillard <veillard redhat com>]

On Wed, Apr 21, 2010 at 04:38:34PM +0200, slyght wrote:
> Hi there,
>
> I recently had an issue with xmlAddChild and xmlCopyNode which I solved but
> still try to understand.
>
> What I did was creating a new subtree and afterwards inserting it into an
> existing tree.
> So after creating a new node and some children I inserted it into the
> existing tree via:
> tmpNodePtr = xmlAddChild(parentNodePtr, xmlCopyNode(newNodePtr, 1));
>
> I used xmlCopyNode because the nodes where newly declared within that
> function and I assumed the pointers would be invalid as soon as I leave that
> function.
>
> The real issue I had was that the namespace of the new node got lost due to
> the copy (tmpNodePtr->ns is NULL). I don't understand why, since I have
> given the option "1" which should do a recursive copy including namespaces.
>
> So now that I removed the xmlCopyNode and instead wrote:
> xmlAddChild(parentNodePtr, newNodePtr);
> everything is fine.
>
> Could someone help me to understand why xmlCopyNode is not working in the
> way I assumed?
>
> By the way: The existing tree and the new subtree should have the same
> namespace, so maybe there's a more clever way to do what I want?

  namespace references are just pointers on elements or attributes to
the actual namespace declaration higher up in the tree. If you copy and
the namespace is not part of that subtree you're likely to loose it
indeed.
  My advice is to not build the subtree in isolation and then graft it
to the target but instead always build it in its context, i.e. passing
the target to the subtree creation. There is contextual references from
a subtree like namespaces and entities, and it's best to avoid moving
stuff if you don't understand perfectly all the data structures
involved.

Daniel

-- 
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