xslt grouping with predefined order

Question

I was looking at the Muenchian method for grouping with xslt,

The data is similar to this

<Root>
  <Entries>
    <Entry Attribute="A"/>
    <Entry Attribute="B"/>
    <Entry Attribute="C"/>
  </Entries>
</Root>

But in addition I needed to have a predefined sort order - on atttributes of my elements. So I was looking at having a custom xml section in the xslt with sort order and inserting it into a variable something like this

<xsl:variable name="sortorder"select="document('')/*/my:data/my:ordering/my:value"/>

Values being e.g. C, B, A which is order and also grouping header

Then it occured to me that instead of using the key() function in the Muenchian method, I could simply loop through the values of the variable.

Like this

<xsl:template match="Entries">
<xsl:for-each select="$sortorder/value">
  <groupheader><xsl:value-of select="."/></groupheader>

... and then apply templates

<xsl:apply-templates select="Entry[@sortattribute=current()"></xsl:apply-templates> 

But I havent gotten it to work. Any tips on how to achieve this? Am I on the right track? I suspect that I am throwing the processor off with the looping over the variable in the context of the <Entry>s but I don't know how to correct it.

Answer 1

Here's a generalized example you could use as a guide:

XML

<input>
    <item category="Winter">Alpha</item>
    <item category="Autumn">Bravo</item>
    <item category="Spring">Charlie</item>
    <item category="Summer">Delta</item>
    <item category="Spring">Echo</item>
    <item category="Autumn">Foxtrot</item>
    <item category="Spring">Golf</item>
    <item category="Summer">Hotel</item>
    <item category="Winter">India</item>
    <item category="Autumn">Juliet</item>
    <item category="Summer">Kilo</item>
    <item category="Winter">Lima</item>
    <item category="Summer">Mike</item>
    <item category="Spring">November</item>
    <item category="Spring">Oscar</item>
    <item category="Autumn">Papa</item>
    <item category="Winter">Quebec</item>
    <item category="Summer">Romeo</item>
    <item category="Spring">Sierra</item>
    <item category="Summer">Tango</item>
    <item category="Spring">Uniform</item>
    <item category="Autumn">Victor</item>
    <item category="Summer">Whiskey</item>
    <item category="Winter">Xray</item>
    <item category="Summer">Yankee</item>
    <item category="Autumn">Zulu</item>
</input>

XSLT 1.0

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:my="http://www.example.com/my"
exclude-result-prefixes="my">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

<my:categories>
    <category>Spring</category>
    <category>Summer</category>
    <category>Autumn</category>
    <category>Winter</category>
</my:categories>

<xsl:variable name="root" select="/"/>

<xsl:template match="/">
    <output>
        <xsl:for-each select="document('')/xsl:stylesheet/my:categories/category">
            <group category="{.}">
                <xsl:apply-templates select="$root/input/item[@category=current()]"/>
            </group>
        </xsl:for-each> 
    </output>
</xsl:template>

<xsl:template match="item">
    <xsl:copy-of select="."/>
</xsl:template>

</xsl:stylesheet>

Result

<?xml version="1.0" encoding="UTF-8"?>
<output>
   <group category="Spring">
      <item category="Spring">Charlie</item>
      <item category="Spring">Echo</item>
      <item category="Spring">Golf</item>
      <item category="Spring">November</item>
      <item category="Spring">Oscar</item>
      <item category="Spring">Sierra</item>
      <item category="Spring">Uniform</item>
   </group>
   <group category="Summer">
      <item category="Summer">Delta</item>
      <item category="Summer">Hotel</item>
      <item category="Summer">Kilo</item>
      <item category="Summer">Mike</item>
      <item category="Summer">Romeo</item>
      <item category="Summer">Tango</item>
      <item category="Summer">Whiskey</item>
      <item category="Summer">Yankee</item>
   </group>
   <group category="Autumn">
      <item category="Autumn">Bravo</item>
      <item category="Autumn">Foxtrot</item>
      <item category="Autumn">Juliet</item>
      <item category="Autumn">Papa</item>
      <item category="Autumn">Victor</item>
      <item category="Autumn">Zulu</item>
   </group>
   <group category="Winter">
      <item category="Winter">Alpha</item>
      <item category="Winter">India</item>
      <item category="Winter">Lima</item>
      <item category="Winter">Quebec</item>
      <item category="Winter">Xray</item>
   </group>
</output>

Note the use of the $root variable to return the context to the input XML document.