How do I access elements from the outer loop from within nested loops?

Question

I have nested xsl:for loops:

<xsl:for-each select="/Root/A">
    <xsl:for-each select="/Root/B">
        <!-- Code -->
    </xsl:for>
</xsl:for>

From within the inner loop, how can I access attributes from the current node in the outer loop?

I keep finding myself writing code like this:

<xsl:for-each select="/Root/A">
    <xsl:variable name="someattribute" select="@SomeAttribute"/>
    <xsl:for-each select="/Root/B">
        <!-- Now can use $someattribute to access data from 'A' -->
    </xsl:for>
</xsl:for>

This doesn't scale very well, as sometimes I need to access several pieces of information and end up creating one variable for each piece. Is there an easier way?

Welbog · Accepted Answer · 2009-01-17 12:53:02Z

26

You can store the entire /Root/A structure in a variable, and make reference to that variable rather than creating a new variable for every attribute and subelement you need to access.

<xsl:for-each select="/Root/A/">
    <xsl:variable name="ROOT_A" select="."/>
    <xsl:for-each select="/Root/B/">
         <!-- Variable is accessed like this: $ROOT_A/@someAttribute
              Just like a normal XML node -->
    </xsl:for-each>
</xsl:for-each>

edited Jan 17, 2009 at 12:53

answered Jan 17, 2009 at 12:44

Welbog

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2 Comments

AnthonyWJones Over a year ago

+1, but it might be worth editing the variable name to make its function more clear.

Marc Gravell Over a year ago

That's what I usually end up doing ;-p

Community · Accepted Answer · 2017-05-23 11:53:16Z

8

Welbog has answered it well - but just to note you appear to be doing a cartesion (cross) join - is that intentional? If you are trying to do a regular join (with a predicate etc), then you want want to look into <xsl:key/> - i.e. declare a key:

<xsl:key name="BIndex" match="/Root/B" use="SomeChildNode"/>

then consume in your predicate:

<xsl:for-each select="/Root/A/">
    <xsl:variable name="ROOT_A" select="."/>
    <xsl:for-each select="key('BIndex', LocalNode)">
     <!-- -->
    </xsl:for-each>
</xsl:for-each>

This should be equivalent to (but much faster than) the predicate:

    <xsl:for-each select="/Root/B[SomeChildNode = current()/LocalNode]">

If you are grouping the data, then look at Muenchian grouping

edited May 23, 2017 at 11:53

CommunityBot

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answered Jan 17, 2009 at 13:00

Marc Gravell

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3 Comments

pauldoo Over a year ago

Thanks for the tips.. I'm relatively new to XSLT and aren't completely sure what I'm doing yet. Once I get things working I'll take a look at what you suggest to see if there's an easier way.

GuruM Over a year ago

Note: It took me some effort to decipher the 'cartesian-join vs. predicate-join part' above. So just noting down the difference for people new to it. Basically if you have a 'm' number of nodes in A and 'n' number of nodes in B, cartesian join will result in m*n nodes whereas predicate-join joins on a particular key i.e. join A AND B where A.key = B.key.

CodeManX Over a year ago

To check against the element name of current (the element the for-loop iterates over), you can use name(current()) - don't try current()/name(), it's not allowed.

Sangeeta · Accepted Answer · 2015-12-10 07:39:26Z

0

The following could also be used :

    <xsl:for-each select="ns:attribute">
        <name><xsl:value-of select="ns:name" /></name>              
        <xsl:for-each select="ns:value">
        <value><xsl:value-of select="."/></value>       
        </xsl:for-each>
    </xsl:for-each>

For parsing the XML document ..

 <ns:attribute>
      <ns:name>name</ns:name>
      <!--1 or more repetitions:-->
      <ns:value>Rahul</ns:value>
      <ns:value>Sushovan</ns:value>
</ns:attribute>

answered Dec 10, 2015 at 7:39

Sangeeta

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