Subject: Re: [xsl] Problems to interpret an attribute value as an Xpath expression From: Jeni Tennison <jeni@xxxxxxxxxxxxxxxx> Date: Thu, 10 Jan 2002 13:39:11 +0000 |
Hi Roman, [Removed www-forms@xxxxxx 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/ XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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