How to know variable has value or not in XSLT

Question

I am creating XSLT file. I have one variable which take value from XML file.But it may happen that there is no reference in xml for the value and at that time XSL variable will return False/None(don't know).I want keep condition like,If there is no value for the variable use the default one. How to do that ?

Answer 1

You haven't explained what you mean by "has no value". Here is a generic solution:

not($v) and not(string($v))

This expression evaluates to true() iff $v "has no value".

Both conditions need to be met, because a string $v defined as '0' has a value, but not($v) is true().

In XSLT 1.0 using a default can be achieved in different ways if the "value" is a node-set or if the value is a scalar (such as a string, a number or a boolean).

@Alejandro provided one way to get a default value if a variable that is supposed to contain a node-set is empty.

If the variable is supposed to contain a scalar, then the following expression returns its value (if it has a value) or (otherwise) the desired default:

concat($v, substring($default, 1 div (not($v) and not(string($v)))))

Answer 2

With the few details given in the question, the simplest test you can do is:

<xsl:if test="$var">
    ...
</xsl:if>

Or you might use xsl:choose if you want to provide output for the else-case:

<xsl:choose>
    <xsl:when test="not($var)"> <!-- parameter has not been supplied -->
</xsl:when>
    <xsl:otherwise> <!--parameter has been supplied --> </xsl:otherwise>
</xsl:choose>

The second example will also handle the case correctly that the variable or parameter has not been supplied with an actual value, i.e. it equals the empty string. This works because not('') returns true.

Answer 3

You can use string-length to check, if a variable called $reference for example contains anything.

<xsl:choose>

  <xsl:when test="string-length($reference) > 0">
    <xsl:value-of select="$reference" />
  </xsl:when>

  <xsl:otherwise>
    <xsl:text>some default value</xsl:text>
  </xsl:otherwise>

</xsl:choose>

If necessary use normalize-space, too.