Subject: RE: How can you tell if a variable exists? From: Kay Michael <Michael.Kay@xxxxxxx> Date: Tue, 2 Nov 1999 09:41:01 -0000 |
> How can you tell if a variable exists (or rather does not > exist), without erroring out of the stylesheet. > > For example: > I am using the SAXON servlet to present HTML to the user. > I am passing in the parameters from doPost to the stylesheet. If the > parameters exist, all is well. But when a parameter does not exist, and is not > passed to the stylesheet, I just get an exception. How do I prevent that? > Referring to $v when there is no <xsl:param name="v"> or <xsl:variable name="v"> in scope is an error, and you can't trap this. But referring to $v when there is a declaration of <xsl:param name="v"> should not give an exception, whether or not the parameter has been given a value. >From the description of your problem, I would declare a global parameter <xsl:param name="v"/> and then in your code you can do <xsl:choose> <xsl:when test="not($v)"> <!-- parameter has not been supplied --> </xsl:when> <xsl:otherwise> <!--parameter has been supplied --> </xsl:otherwise> </xsl:choose> The reason this works is that when no actual parameter v is supplied, it takes its default value, which in this case is an empty string (because the xsl:param has no select expression or content), and the test not($v) returns true if $v is an empty string. Mike Kay XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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