Conditional position-check in XSLT

I have an XSLT file which renders articles. I'm passing a variable into the XSLT file which is supposed to limit the number of records output. The trouble is, this 'limit' variable is optional - if it's not there the XSLT file needs to output all values; if the 'limit' variable is a number, then it needs to only output that 开发者_开发技巧number of items (presumably using a position() test).

Here's my code:

<xsl:variable name="limit" select="/macro/limit"/>

<xsl:template match="/">
  <xsl:variable name="allNodes" select="$localSiteRoot/descendant-or-self::*[articles != '']"/>
  <xsl:for-each select="$allNodes">

    <div class="articleItem">
      <h3><xsl:value-of select="./articleHeader"/></h3>
      <xsl:if test="./articleSubheader != ''">
        <h4><xsl:value-of select="./articleSubheader"/></h4>
      </xsl:if>
    </div>

  </xsl:for-each>
</xsl:template>

Clearly I could just do an XSLT choose around this and say

<xsl:choose>
  <xsl:when select="$limit!= ''">
    <xsl:if test="position() &lt; $limit">

But then I'd need to repeat the code twice. There must be a better way, perhaps using templates, but I just can't figure out how it would work and my XSLT isn't great.

Could anyone point me in the right direction with the best/neatest way to approach this?

Thanks!

Just use:

<xsl:for-each select="$allNodes[not(position() > $limit)]"> 

Explanation:

1. If the value of $limit is castable to a number, then the expression in the select attribute above selects not more than $limit nodes.

2. If the value of $limits isn't castable to a number (e.g. empty or 'abc') then it is converted to NaN. By definition comparisons involving NaN are always false(), therefore the predicate not(position() > $limit is true() and in this case all nodes in $allNodes are selected.