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Re: Problems to interpret an attribute value as an Xpath expression
- From: Jeni Tennison <jeni at jenitennison dot com>
- To: xsl-list at lists dot mulberrytech dot com
- Date: Thu, 10 Jan 2002 13:39:11 +0000
- Subject: Re: [xsl] Problems to interpret an attribute value as an Xpath expression
- Organization: Jeni Tennison Consulting Ltd
- References: <0C79A363CB0321418927D0CB1AD0403C08A874@hicoetsrv000006.hico.local>
- Reply-to: xsl-list at lists dot mulberrytech dot com
Hi Roman,
[Removed www-forms@w3.org from the CC list because we're not allowed
to cross-post on this list.]
> I'd like to use the value of a ref attribute as an XPath expression
> in my stylesheet. I want the processor to jump to the specified node
> and get the value from there. I used a "normal" <xsl:value-of
> select="@ref"/> ,but the processor didn't interpret it as an XPath
> expression but as a string.
>
> Does anyone know a method to tell the processor to use a source
> document's attribute value as an XPath expression in the stylesheet?
You can't do it in XSLT 1.0. Some processors support an extension
evaluate() function, so that you can do, for example:
saxon:evaluate(concat('/xform:model/xform:instance', @ref))
Another alternative that might be feasible would be to construct a
path to the nodes that you want to refer to and use that as a key
value. This is difficult because key values have to be set using XPath
expressions, but it's doable if you're using a processor that supports
user-defined extension functions written in XSLT. For example, you
could do:
<xsl:key name="instance-data" match="xform:instance//*"
use="my:path()" />
Where my:path was defined with something along the lines of:
<func:function name="my:path">
<func:result select="concat(my:path(..), '/', name())" />
</func:function>
You could then use:
key('instance-data', concat('xform:model/xform:instance', @ref))
to get hold of the relevant node from the instance data tree.
A third alternative might be feasible if the processor you're using
supports XPointer fragment identifiers in URLs. You might be able to
do something like:
document(concat('#xpointer(/xform:model/xform:instance', @ref, ')'),
/)
to get hold of the node that you want.
[This was one of the use cases that I pointed out for an evaluate()
function in XPath 2.0.]
Cheers,
Jeni
---
Jeni Tennison
http://www.jenitennison.com/
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