Code Answer: How do I check if a tag exists in XSLT?

I have the following template

<h2>one</h2>
<xsl:apply-templates select="one"/>
<h2>two</h2>
<xsl:apply-templates select="two"/>
<h2>three</h2>
<xsl:apply-templates select="three"/>

I would like to only display the headers (one,two,three) if there is at least one member of the corresponding template. How do I check for this?

From stackoverflow Manu

<xsl:if test="one">
  <h2>one</h2>
  <xsl:apply-templates select="one"/>
</xsl:if>
<!-- etc -->

Alternatively, you could create a named template,

<xsl:template name="WriteWithHeader">
   <xsl:param name="header"/>
   <xsl:param name="data"/>
   <xsl:if test="$data">
      <h2><xsl:value-of select="$header"/></h2>
      <xsl:apply-templates select="$data"/>
   </xsl:if>
</xsl:template>

and then call as:

  <xsl:call-template name="WriteWithHeader">
    <xsl:with-param name="header" select="'one'"/>
    <xsl:with-param name="data" select="one"/>
  </xsl:call-template>

But to be honest, that looks like more work to me... only useful if drawing a header is complex... for a simple <h2>...</h2> I'd be tempted to leave it inline.

If the header title is always the node name, you could simplifiy the template by removing the "$header" arg, and use instead:

<xsl:value-of select="name($header[1])"/>

From Marc Gravell

I like to exercise the functional aspects of XSL which lead me to the following implementation:

<?xml version="1.0" encoding="UTF-8"?>

<!-- test data inlined -->
<test>
    <one>Content 1</one>
    <two>Content 2</two>
    <three>Content 3</three>
    <four/>
    <special>I'm special!</special>
</test>

<!-- any root since take test content from stylesheet -->
<xsl:template match="/">
    <html>
        <head>
            <title>Header/Content Widget</title>
        </head>
        <body>
            <xsl:apply-templates select="document('')//test/*" mode="header-content-widget"/>
        </body>
    </html>
</xsl:template>

<!-- default action for header-content -widget is apply header then content views -->
<xsl:template match="*" mode="header-content-widget">
    <xsl:apply-templates select="." mode="header-view"/>
    <xsl:apply-templates select="." mode="content-view"/>
</xsl:template>

<!-- default header-view places element name in <h2> tag -->
<xsl:template match="*" mode="header-view">
    <h2><xsl:value-of select="name()"/></h2>
</xsl:template>

<!-- default header-view when no text content is no-op -->
<xsl:template match="*[not(text())]" mode="header-view"/>

<!-- default content-view is to apply-templates -->
<xsl:template match="*" mode="content-view">
    <xsl:apply-templates/>
</xsl:template>

<!-- special content handling -->
<xsl:template match="special" mode="content-view">
    <strong><xsl:apply-templates/></strong>
</xsl:template>

Once in the body all elements contained in the test element have header-content-widget applied (in document order).

The default header-content-widget template (matching "*") first applies a header-view then applies a content-view to the current element.

The default header-view template places the current element's name in the h2 tag. The default content-view applies generic processing rules.

When there is no content as judged by the [not(text())] predicate no output for the element occurs.

One off special cases are easily handled.

From $pageUsers[$post.author].name

Code Answer

Saturday, February 12, 2011

How do I check if a tag exists in XSLT?

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