<xsl:for-each>

The last of the control flow elements, <xsl:for-each>, has already been seen in action when we were counting the number of scenes in each act. Here is the stylesheet (count.xsl) that we used:

The <xsl:for-each> statement effectively allows us to embed a template inside another. Instead of the <xsl:for-each> statement, we could have used <xsl:apply-templates>, and made the contents of the <xsl:for-each> a separate template:

So when should you use <xsl:for-each> and when should you use <xsl:apply-templates>? Often, the same template will be executed as a result of several XPath expression matches. In this case, using <xsl:apply-templates> provides re-usability in the same way that a function call does in a procedural language. On other occasions, it is largely a matter of style, and you should use whichever makes your stylesheet easier to understand. As we saw earlier, a push model stylesheet tends to use <xsl:apply-templates> most of the time to execute specific template rules as elements are found in the source tree, while a pull model is more likely to have a single large template with <xsl:for-each> statements to execute the embedded rule at a specific point in the stylesheet.

XSLT has the concept of a context node, which is important when using relative XPath expressions. In the stylesheet above, the line:

sets the context node to the <ACT> element. In the following line:

the expression is relative to this context node. There are two ways of changing the context node in XSLT: <xsl:template> is one, and <xsl:for-each> is the other. These are the only ways of changing the context node. Using an XPath expression in a test attribute, for example, does not do this.