CODEWITHSUNDEEP
xmlxsltxslt-2.0xslt-3.0
mdr
mdr

Reputation: 197

How can I use an XSLT variable containing a pattern in a template match expression

I would like to do

<xsl:variable name="myPattern" select="node1|node2"/>
<xsl:template match="$myPattern">
    ...
</xsl:template>
<xsl:template  match="/">
    ...
    <xsl:for-each select="distinct-values(//$myPattern/name/text()">
        ...
    </xsl:for-each>
</xsl:template>

I tried this with XSLT version 2.0 and 3.0 to no avail. Any hints?

Reason: The pattern is a little more complicated and I would like to use it in several places and not just this match.

EDIT:

I solved my problem for now by accepting the fact that the variable does not contain the string/pattern, but the result nodes. If I modify it to

<xsl:variable name="myNodes" select="//(node1|node2)"/>
<xsl:template match="$myNodes">
    ...
</xsl:template>
<xsl:template  match="/">
    ...
    <xsl:for-each select="distinct-values($myNodes/name/text()">
        ...
    </xsl:for-each>
</xsl:template>

it works fine.

I still wonder why it is not possible to simply store the string in the variable and use it wherever literal strings are allowed.

Upvotes: 0

Views: 2076

Answers (2)

Martin Honnen
Martin Honnen

Reputation: 167716

As for textual replacement, with XSLT 3.0 you can use use a static parameter with a string value and then so called shadow attributes (https://www.w3.org/TR/xslt-30/#shadow-attributes):

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:math="http://www.w3.org/2005/xpath-functions/math" exclude-result-prefixes="xs math"
    version="3.0">

    <xsl:param name="myPattern" static="yes" as="xs:string" select="'node1|node2'"/>

    <xsl:template _match="{$myPattern}">
        <matched name="{node-name()}">
            <xsl:apply-templates/>
        </matched>
    </xsl:template>

    <xsl:template match="/*">
        <xsl:copy>
            <xsl:for-each _select="distinct-values(//{$myPattern}/text())">
                <value>
                    <xsl:value-of select="."/>
                </value>
            </xsl:for-each>
            <xsl:apply-templates/>
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

That transforms 

<root>
    <node1>a</node1>
    <node2>1</node2>
    <node1>a</node1>
</root>

into 

<root><value>a</value><value>1</value>
        <matched name="node1">a</matched>
        <matched name="node2">1</matched>
        <matched name="node1">a</matched>
</root>

In XSLT 3.0 you can use a variable or parameter reference for the match pattern of a template but it is not a textual replacement that happens, rather "$xyz matches any node that is present in the value of the variable $xyz" (https://www.w3.org/TR/xslt-30/#pattern-examples).

So with the XSLT being 

<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions">
    <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

    <xsl:param name="delete" select="//*[contains-token(@class, 'foo')]"/>

    <xsl:mode on-no-match="shallow-copy"/>

    <xsl:template match="$delete"/>

</xsl:stylesheet>

and the XML input being 

<html>
    <head>
        <title>test</title>
    </head>
    <body>
        <p class="foobar bar">Paragraph 1.</p>
        <p class="foo bar">Paragraph 2.</p>
        <p class="bar">Paragraph 3.</p>
        <p class="foo">Paragraph 4.</p>
    </body>
</html>

a conforming XSLT 3.0 processor like Saxon 9.7 EE outputs 

<html>
    <head>
        <title>test</title>
    </head>
    <body>
        <p class="foobar bar">Paragraph 1.</p>

        <p class="bar">Paragraph 3.</p>

    </body>
</html>

Upvotes: 2

Michael Kay
Michael Kay

Reputation: 163595

I would suggest using a function rather than a variable:

<xsl:function name="_:myPattern" as="xs:boolean">
  <xsl:param name="node" as="node()"/>
  <xsl:sequence select="self::node1() | self::node2()"/>
</xsl:function>

<xsl:template match="node()[_:myPattern(.)]">
 ...
</xsl:template>

Upvotes: 3

Related Questions