xsl:call-template

 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.