xslt variable scope and its usage

I am learning xslt and had one question about how can i use xslt variable in diff. for each loop. I know xslt isn't a procedural language so variable declared in for loop cannot be accessed in another loop. But is there any way I can just declare global variable then assign some value in first for loop and use that variable in second for loop?

Any ideas would be highly appreciated.

Thanks

回答1:

is there any way I can just declare global variable then assign some value in first for loop and use that variable in second for loop?

The way to assign value to an xsl:variable (of course this is only initialization) from within an xsl:for-each, is to include the xsl:for-each in the body of the variable.

Here is a complete example:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="/*">
     <xsl:variable name="vMax">
       <xsl:for-each select="num">
        <xsl:sort data-type="number" order="descending"/>

        <xsl:if test="position() = 1">
         <xsl:value-of select="."/>
        </xsl:if>
       </xsl:for-each>
     </xsl:variable>

     Values close to the maximum:
<xsl:text/>

       <xsl:for-each select="num">
        <xsl:if test="not($vMax - . > 3) ">
         <xsl:value-of select="."/>
         <xsl:text>&#xA;</xsl:text>
        </xsl:if>
       </xsl:for-each>
 </xsl:template>
</xsl:stylesheet>

When this transformation is applied on the following XML document...

<nums>
  <num>01</num>
  <num>02</num>
  <num>03</num>
  <num>04</num>
  <num>05</num>
  <num>06</num>
  <num>07</num>
  <num>08</num>
  <num>09</num>
  <num>10</num>
</nums>

...it first defines a vMax variable that gets its value from the xsl:for-each contained in its body.

Then the vMax variable is used in the second xsl:for-each to output all numbers that are "close" to the so computed maximum.

The wanted, correct result is produced:

     Values close to the maximum:
07
08
09
10

It is also possible to simulate "assigning" a variable with different values by using a recursively called named template and pass the "new value" as parameter to the called template.

Here is an example showing this technique. Here we are calculating the maximum of values, contained in nodes of a node-set. Every time we access the next node in the node-set, the current maximum is compared to this value and if necessary the new maximum becomes the value of the next node. We then call the same template recursively, passing as the value of the current maximum the new maximum:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="/*">
  <xsl:call-template name="max">
    <xsl:with-param name="pList" select="*"/>
  </xsl:call-template>
 </xsl:template>

 <xsl:template name="max">
   <xsl:param name="pMax" select="-99999999"/>
   <xsl:param name="pList"/>

   <xsl:choose>
     <xsl:when test="$pList[1]">
       <xsl:variable name="vnewMax" select=
       "$pMax * ($pMax >= $pList[1])
       +
        $pList[1] * not($pMax >= $pList[1])
       "/>

       <xsl:call-template name="max">
        <xsl:with-param name="pMax" select="$vnewMax"/>
        <xsl:with-param name="pList" select="$pList[position() > 1]"/>
       </xsl:call-template>
     </xsl:when>
     <xsl:otherwise>
       <xsl:value-of select="$pMax"/>
     </xsl:otherwise>
   </xsl:choose>
 </xsl:template>
</xsl:stylesheet>

When this transformation is applied to the same XML document (above), the wanted, correct result is produced:

回答2:

xsl:for-each is not a loop in the sense for or foreach loops exist in procedural languages so any question talking about loops is difficult to understand and more difficult to answer.

If you want to use global variables in XSLT you can do so but you would bind a value to the variable where you declare it (i.e. globally), you can't assign a value later on in a for-each as you seem to want to do.

回答3:

you have written, 'XSL is a procedural lang' .. Well, its not. It is a Declarative Language ..
Variable is assigned along with its declaration, variables don't change!
Usually we follow recursive call for templates using call-template passing params to them .. (this works like recursive function calling with passing arguments in procedural languages)
That is one method to handle counts and conditional looping etc ..

We would be happy to help you incase if you mention the exact scenario with Sample XML, and the output you are expecting out of it :)