RE: [xsl] Help with some XPATH questions

Subject: RE: [xsl] Help with some XPATH questions
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Thu, 28 Jul 2005 22:18:44 +0100
> So far what I have is 
> 
>             <RESULTSET>
>                 <xsl:attribute name="FOUND">
>                     <xsl:value-of 
> select="count(//LayoutCatalog/Layout)"/>
>                 </xsl:attribute>
>                 <xsl:apply-templates 
> select="//LayoutCatalog/Layout/descendant::Object[@type='text']"/>
>             </RESULTSET>
> 
> 
> I thought that this would work but it does not... this is the 
> error I get:
> 
> Description: E Error in expression 
> //LayoutCatalog/Layout/descendant::Object[@type='text']: Axis 
> in pattern must be child or attribute

It's a bad error message because it says first that it's an error in an
expression and then that it's an error in a pattern, and expressions and
patterns are quite different things. But it's patterns that don't allow axes
other than child or attribute, so that's almost certainly what it's
referring to. The select attribute of apply-templates is not a pattern, it's
an expression. Your error is probably that you have used a similar construct
in an <xsl:template match="XXX"> context, where it is not allowed.

In a match pattern you can't write A/descendant::B, but you can write A//B
which usually means the same thing. (The cases where it doesn't are where B
is followed by a numeric predicate).
> 
> I guess what I don't understand this error - and I also don't 
> really understand the role of
> 
> "<xsl:attribute name="FOUND">"

Your code snippet creates a RESULTSET element, with a FOUND attribute whose
value is the number of //LayoutCatalog/Layout elements in the source
document, with the content of the element being computed by the template
that matches the selected Object elements.

You could also have written this as:

<RESULTSET FOUND="{count(//LayoutCatalog/Layout)}">
  <xsl:apply-templates
select="//LayoutCatalog/Layout//Object[@type='text']"/>
</RESULTSET>

Michael Kay

Current Thread