How to change or reassign a variable in XSLT?

问题:

How can I reassign a value to a variable previously assigned? I need it to works like this:

<xsl:variable name="variable2" select="'N'" />
....
<xsl:when test="@tip = '2' and $variable2 != 'Y'">                                                   
    <xsl:variable name="variable2" select="'Y'" />
</xsl:when>

回答1:

Variables in XSLT may only be assigned a value once. This is done by design. See Why Functional languages? for an appreciation of the motivation in general.

Rather than reassign a variable, write conditionals against the input document directly, or call a function (or named template) recursively with varying local parameters.

Anything you need to do can be done with an approach that does not require reassignment of variables. To receive a more specific answer, provide a more specific question.

See also:

• In XSLT how do I increment a global variable from a different scope?
• Increment a value in XSLT
• Use recursion effectively in XSL

回答2:

Just use multiple variables. Here's your example made to work...

    <xsl:variable name="variable1" select="'N'" />
    ....
    <xsl:variable name="variable2">
        <xsl:choose>
            <xsl:when test="@tip = '2' and $variable1 != 'Y'">
                <xsl:value-of select="'Y'" />
            </xsl:when>
            <xsl:otherwise>
                <xsl:value-of select="$variable1" />
            </xsl:otherwise>
        </xsl:choose>
    </xsl:variable>

回答3:

You cannot - 'variables' in XSLT are actually more like constants in other languages, they cannot change value.

回答4:

Reassignable variables can be declared using an accumulator, available from XSLT version 3.0. :

    <?xml version="1.0" encoding="UTF-8"?>
    <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="3.0" >
      <xsl:mode use-accumulators="variable2" streamable="no"/>
      <xsl:output omit-xml-declaration="no" indent="yes"/>

      <xsl:accumulator name="variable2" initial-value="'N'">
       <xsl:accumulator-rule match="Inpayment" select="if ($value = 'N' and @tip = '2') then 'Y' else 'N' "/>
      </xsl:accumulator>

      <xsl:template match="node()|@*">
        <xsl:copy>
          <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
      </xsl:template>

      <xsl:template match="Inpayment">
        <xsl:copy>
          <xsl:apply-templates select="@*"/>
          <xsl:value-of select="accumulator-before('variable2')"/>
          <xsl:apply-templates select="node()"/>
        </xsl:copy>
      </xsl:template>

    </xsl:stylesheet>