Question

I’m extracting the value of a node into a variable:

<xsl:variable name="UPC" select="//x:input[@name='field-keywords']/@value"/>
<xsl:value-of select="$UPC" />  <!-- This works! -->

Then I want to query another XML document for a node with the same value:

<xsl:value-of select="document('price_list.xml')/im_prices/row/UPC_Code[text()='$UPC']"/>

When I substitute $UPC for the actual value I find the node just fine, but when I use $UPC it doesn’t work.

I haven’t been able to work out how to extract the value to a variable and use it in a future xpath query.

Answer 1

Just remove the apostrophes — in your expression you compare to the literal “$UPC”:

 <xsl:value-of select=
   "document('price_list.xml')
        /im_prices/row/UPC_Code[text()=$UPC]"/>

There is something more to be said about this question:

I’m extracting the value of a node into a variable:

 <xsl:variable name="UPC" select="//x:input[@name='field-keywords']/@value"/>

No, this doesn’t “extract the value” — the variable’s value is a set of nodes, aka nodeset.

Also, do note that this nodeset in general has more than one node.

 <xsl:value-of select="$UPC"/>  <!-- This works! -->

This outputs the string value of the first node contained in the variable $UPC.

Then I want to query another XML document for a node with the same value:

     <xsl:value-of select="document('price_list.xml')/im_prices/row/UPC_Code[text()='$UPC']"/>

Even if the apostrophes are removed, the above outputs the string value of the first of the document('price_list.xml')/im_prices/row/UPC_Code elements that has a text node child whose string value is equal to the string value of one of the nodes contained in the variable $UPC.