The <xsl:call-template> element in XSLT (Extensible Stylesheet Language Transformations) is used to invoke a named template defined within the XSLT stylesheet. It allows you to reuse a specific piece of XSLT code (a template) at multiple places within your stylesheet. Here's a detailed explanation of how <xsl:call-template> works:
Basic Syntax:
<xsl:call-template name="TemplateName"/>
name Attribute: Specifies the name of the template to be called. The XSLT processor will search for a template with this name in the current stylesheet and execute its content.
Behavior:
Template Invocation:
When <xsl:call-template> is encountered during the XSLT transformation, the processor searches for a template in the stylesheet with the specified name (TemplateName in the example above).
Parameter Passing (Optional):
You can pass parameters to the called template by using <xsl:with-param> elements inside <xsl:call-template>.
<xsl:call-template name="TemplateName">
<xsl:with-param name="paramName" select="paramValue"/>
</xsl:call-template>
In the called template, you can access the passed parameters using <xsl:param> elements.
<xsl:template name="TemplateName">
<xsl:param name="paramName"/>
<!-- Template content using $paramName -->
</xsl:template>
Use Cases:
Reusable Code:
<xsl:call-template> allows you to create reusable code snippets in the form of templates. These templates can then be called wherever needed in the stylesheet.
<xsl:template name="formatDate">
<xsl:param name="date"/>
<xsl:value-of select="substring($date, 1, 10)"/>
</xsl:template>
<!-- Usage -->
<xsl:call-template name="formatDate">
<xsl:with-param name="date" select="someDateNode"/>
</xsl:call-template>
In this example, the formatDate template can be called multiple times to format different date values.
Modularization:
<xsl:call-template> allows you to modularize your XSLT stylesheets. You can divide complex transformations into smaller, manageable templates and call them when needed.
Conditional Logic:
It enables the application of different templates based on conditions.
<xsl:choose>
<xsl:when test="someCondition">
<xsl:call-template name="templateForCondition"/>
</xsl:when>
<xsl:otherwise>
<xsl:call-template name="defaultTemplate"/>
</xsl:otherwise>
</xsl:choose>
Here, the appropriate template is called based on the value of someCondition.
Note:
<xsl:call-template> is often used in conjunction with <xsl:template> and <xsl:param> elements to create flexible and modular stylesheets.
It's essential to ensure that the named template exists in the same XSLT stylesheet where <xsl:call-template> is used; otherwise, an error will occur during the transformation process.
In summary, <xsl:call-template> provides a way to create modular, reusable, and conditionally applicable transformations in XSLT stylesheets, enhancing the maintainability and readability of XSLT code.
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