Loops and output¶

Two instructions do most of the day-to-day work in a stylesheet: xsl:for-each to iterate, and xsl:value-of to write text.

xsl:value-of¶

xsl:value-of evaluates an XPath expression and inserts its string value into the result tree.

<xsl:value-of select="title"/>     <!-- text of the child <title>      -->
<xsl:value-of select="."/>         <!-- text of the current node       -->
<xsl:value-of select="@id"/>       <!-- value of the id attribute       -->
<xsl:value-of select="price * 2"/> <!-- XPath can compute, too          -->

If the expression selects several nodes, only the first is output. To emit all of them, loop.

xsl:for-each¶

xsl:for-each processes every node in a selected set, running its body once per node. Inside the loop the current node is the node being processed, so relative paths like title resolve against it.

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<xsl:for-each select="catalog/cd">
  <div>
    <span style="font-weight:bold"><xsl:value-of select="title"/></span>
    — <xsl:value-of select="artist"/>
    (<xsl:value-of select="price"/>)
  </div>
</xsl:for-each>

Run against the catalog this produces one div per CD:

Literal result elements and attributes¶

Anything in the stylesheet that is not in the xsl: namespace is copied to the output verbatim — <div>, <span>, style="…" and so on. These are literal result elements.

When you need a computed attribute value, you cannot just write <td bgcolor="{...}"> blindly — but you can with an attribute value template: an XPath expression in curly braces inside an attribute.

<!-- the class attribute is filled in from the data -->
<tr class="cd-{position()}">
  <td><xsl:value-of select="title"/></td>
</tr>

position() is an XPath function giving the 1-based index of the current node within the loop — handy for striping rows or numbering items.

Next¶

The expressions used for output are often repeated or worth naming. Variables show how to bind those values, why an XSLT variable cannot be reassigned, and how its scope follows the stylesheet structure.