Named Templates

Mike Brown

Updated from the vellum orginal (DaveP).

To pass a variable to a called
template, you need to use with-param and param , like this:

<xsl:template match="/">
    <xsl:variable name="DebugOpts" select="abc123"/>
    <xsl:call-template name="childTemplate">
        <xsl:with-param name="DebugOpts" select="$DebugOpts"/>
    </xsl:call-template>
</xsl:template>

<xsl:template name="childTemplate">
    <xsl:param="DebugOpts" select="."/>
    <xsl:text>The value of $DebugOpts is: </xsl:text>
    <xsl:value-of select="$DebugOpts"/>
</xsl:template>

This technique can be used to pass parameters back and forth between
templates. An increment function could be simulated this way.
            

Colin Paul Adams, David Carlisle

This is used extensively in FXSL for XSLT2.

Where a test does not require any source document, then the initial template is defined like:

<xsl:template match="/" name="initial"> etc.

Then you can invoke the test from the command line, without having to supply a source XML document.

But if this is not convenient, so the match ="/" is retained for this purpose.

DC adds

I use it sometimes. suppose you have two elements in your source <foo>xxx</foo> and <bar>xxx</bar> and you want foo to generate the same output as bar except that it has to be surrounded by <div class="foo"> ...</div>.

One way is to have

<xsl:template match="bar" name="bar">
 <span><xsl:apply-templates/></span>
</xsl:template>

<xsl:template match="foo">
 <div class="foo"><xsl:call-template name="bar"/></div> </xsl:template>

Of course, there are other ways to achieve this, but still this idiom comes in handy sometimes.

Dave Tucker offers

I use this capability to write templates where the first invocation comes from matching some source element, and subsequent invocations are from recursive calls. For example:

  <xsl:template match="insert-events" name="insert-events">
    <xsl:param name="days-from-now">0</xsl:param>

    <xsl:if test="$days-from-now &lt; 7">
      <!-- process this day -->
      <!-- ... -->

      <!-- recursively call insert-event for next day -->
      <xsl:call-template name="insert-events">
        <xsl:with-param name="days-from-now" select="$days-from-now + 1"/>
      </xsl:call-template>
    </xsl:if>
  </xsl:template>

Notice that this pattern also relies on having default parameter values.