CODEWITHSUNDEEP
xsltxslt-1.0
Stroboskop
Stroboskop

Reputation: 4356

Updating variables in XSL

Is there any way in XSL to update a global variable?

I want to check what elements i already transformed and act accordingly. That would require me to somehow add the names of the elements to some sort of list and update it each time a new element is transformed.

But since xsl:variable isn't "variable" in the sense one would expect, i have no way of adding anything to it once it has been defined.

I have multiple included data files, so using xsl functions that only know the current set of nodes will not help.

== Edit ==

This is what my transformation looks like now. But it will include files that are repeatedly referenced in different sub-files every time.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <xsl:output method="xml" />

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

    <!-- include the contents of referenced files -->
    <xsl:template match="reference">
        <xsl:apply-templates select="document(@url)/data/node()" />
    </xsl:template>

</xsl:transform>

And the data files would look something like this:

<data>
    <reference url="another_data_file.xml"/>
    ... other stuff ...
</data>

Upvotes: 2

Views: 6897

Answers (4)

markusk
markusk

Reputation: 6667

XSLT is a functional language, and does not allow variables to be updated. If you need to aggregate results over several steps, the usual approach is to use a recursive template. Example:

<xsl:template name="transform-elements">
    <xsl:param name="elements-to-process" select="/.."/>
    <xsl:param name="processed-elements" select="/.."/>
    <xsl:if test="$elements-to-process">
        <xsl:variable name="element" select="$elements-to-process[1]"/>

        <!-- ... Do stuff with $element ...-->

        <!-- Recursively invoke template for remaining elements -->
        <xsl:call-template name="transform-elements">
            <xsl:with-param name="elements-to-process" 
                            select="$elements-to-process[position() != 1]"/>
            <xsl:with-param name="processed-elements" 
                            select="$processed-elements|$element"/>
        </xsl:call-template>
    </xsl:if>
</xsl:template>

Upvotes: 8

newtover
newtover

Reputation: 32094

I am not sure about the size of the documents you are trying to parse, but as a solution for relatively small XML documents you can output the result to a variable and having applied the extension function node-set (from exslt, or msxsl, etc.) apply transformation to the contents of the variable, excluding duplicate nodes as if you would process a single XML document.

Upvotes: 0

Dirk Vollmar
Dirk Vollmar

Reputation: 176159

If your input data is spread over several documents it might be a good idea to split the transformation process into several steps.

Add a pre-processing transformation which pulls the relevant sections from the input documents into a single intermediate document. This document can then be transformed with a simple XSLT and you might not run into the problems which you are currently facing.

Upvotes: 1

Russ Clarke
Russ Clarke

Reputation: 17909

Sadly, there isn't a direct way, XSL Variables are Assign Once only, but that can be assigned conditionally.

However, variables defined in a block are only accessible to that block and its children, perhaps inverting your logic and doing it iteratively would work instead ?

That way, you can't process stuff that's been transformed already, as it's already been completed.

Have a look into the usages of xsl:Key and xsl:for-each, this will let you order the nodes you transform.

To quote from w3schools, using this XML:

<persons>
  <person name="Tarzan" id="050676"/>
  <person name="Donald" id="070754"/>
  <person name="Dolly" id="231256"/>
</persons>

And this XSL:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:key name="preg" match="person" use="@id"/>

<xsl:template match="/">
  <html>
  <body>
  <xsl:for-each select="key('preg','050676')">
    <p>
    Id: <xsl:value-of select="@id"/><br />
    Name: <xsl:value-of select="@name"/>
    </p>
  </xsl:for-each>
  </body>
  </html>
</xsl:template>

</xsl:stylesheet>

Will find the person with the ID of '050676'. Perhaps using this method with more defined key would give you the structure you need?

Upvotes: 1

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