XSLT, 2nd Edition

Passing Parameters

If we invoke a template by name, which is similar to calling a subroutine, we’ll need to pass parameters to those templates. We do this with the <xsl:with-param> element. For example, let’s say we want to call a template named draw-box, and then pass the parameters startX, startY, endX, and endY to it. Here’s what we’d do:

<xsl:call-template name="draw-box">
  <xsl:with-param name="startX" select="50"/>
  <xsl:with-param name="startY" select="50"/>
  <xsl:with-param name="endX" select="97"/>
  <xsl:with-param name="endY" select="144"/>
</xsl:call-template>

In this sample, we’ve called the template named draw-box with the four parameters we mentioned earlier. Notice that up until now, <xsl:call-template> has always been an empty tag; here, though, the parameters are the content of the <xsl:call-template> element. (If you want, you can do the same thing with <xsl:apply-templates>.)

If we’re going to pass parameters to a template, we have to set up the template so that it expects the parameters we’re passing. To do this, we’ll use the <xsl:param> element inside the template. Here are some examples:

<xsl:template name="draw-box">
  <xsl:param name="startX"/>
  <xsl:param name="startY" select="'0'"/>
  <xsl:param name="endX"> 
    10
  </xsl:param>
  <xsl:param name="endY">
    10
  </xsl:param>
  ...
</xsl:template>

A couple of notes about the <xsl:param> element:

• If you define any <xsl:param> elements in a template, they must be the first thing in the template.

• The <xsl:param> element allows you to define ...