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¶

Output often needs to depend on the data — highlight expensive CDs, skip empty fields. That is the job of conditionals.