print to screen only when a value is different from the preceding value - XSLT

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Thomas Kahn 602 posts 506 karma points

Nov 27, 2009 @ 16:19
0

Print to screen only when a value is different from the preceding value?
Hi!

Let's say I have an XML-structure that looks like this:
```
<person>
<name>Jakob</name>
<title>Art Director</title>
</person>

<person>
<name>Lea</name>
<title>Art Director</title>
</person>

<person>
<name>Jonas</name>
<title>Project Manager</title>
</person>

<person><name>Thomas</name>
<title>Web Developer</title>
</person>

<person>
<name>Johan</name>
<title>Web Developer</title>
</person>
```
Using XSLT I print these persons using a for-each loop. I want the name of the person to be printed every time, but I want to use the title as a header to group the persons I'm listing. The result I want on the screen is:

Art Director
Jakob
Lea

Project Manager
Jonas

Web Developer
Thomas
Johan

How would I accomplish this using XSLT? Is there a way to track if the present value in the loop is different from the previous value and if it is, print it to screen. I suspect the solution involves using calling another template, but I'm having a hard time finding the best solution.

Thanks in advance!

/Thomas Kahn
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Bert 128 posts 251 karma points

Nov 27, 2009 @ 16:43

Can't you adapt the data structure?

<function name="Web Developer">
   <person name="Johan" />
   <person name="Sam" />
</function>
<function ... </function>

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bob baty-barr 1180 posts 1294 karma points MVP

Nov 27, 2009 @ 17:15

0

you could run a nested for each... where you list the <title> when the position is equal to 1

then insided that for each list the <name> where title = currentTitle --

hope that makes sense.

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Chriztian Steinmeier 2800 posts 8791 karma points MVP 8x admin c-trib

Nov 27, 2009 @ 21:58
1
Hi Thomas,

If your data is already sorted by title (which your short fragment suggests) then the following template will be sufficient:
```
   <xsl:template match="person">
        <xsl:if test="preceding-sibling::person[1]/title != title or not(preceding-sibling::person[1])">
            <h2>
                <xsl:value-of select="title" />
            </h2>
        </xsl:if>
        <p>
            <xsl:value-of select="name" />
        </p>
    </xsl:template>
```
If that's not the case, you'll have to dive into "grouping" which can be quite a hassle in XSLT 1.0... let us know, if so.

/Chriztian
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Thomas Kahn 602 posts 506 karma points

Nov 27, 2009 @ 22:21

0

Chriztian, I think your example could work! The nodes are not sorted in any specific order in Umbraco, but in the XSLT I sort them by title and that should be enough.

Will try it first thing on Monday!

/Thomas

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Thomas Kahn 602 posts 506 karma points

Nov 30, 2009 @ 10:48

0

Chriztian - you just saved me a lot of headaches!
It worked like a charm - thanks!

/Thomas K

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Thomas Kahn 602 posts 506 karma points

Nov 30, 2009 @ 11:29

0

Hmm, I guess I jumped the gun there.
This solution works if the nodes are ordered in the correct order in the umbraco backend. In my case they are not - I use a sort select in my XSLT to sort the nodes in the correct order.

So it seems that preceding-sibling::node[1] ignores any sorting directives in the XSLT and uses the order the nodes have in Umbraco.

Bummer. Is there a way to get around this?

/Thomas Kahn

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Thomas Kahn 602 posts 506 karma points

Nov 30, 2009 @ 12:05
0
This was new to me:

"The axis works on the XML source's internal tree-representation (the XSLT processor builds the tree before applying a stylesheet). Therefore,
when you say "xsl:sort", it just begins to process the nodes in the order you specify, sorting can't affect any axis processing."

http://p2p.wrox.com/xslt/3040-sorting-preceding-sibling.html

This page contains a suggestion how to solve the problem by copying the sorted nodes to a new node set. In my code it looks like this:
```
<xsl:variable name="sortedNodeSet">
    <xsl:for-each select="$currentPage/descendant::node">
       <xsl:sort select="data[@alias='competitionStatus']" order="descending"/>
        <xsl:sort select="@nodeName" order="ascending"/>
        <xsl:copy-of select="."/>
   </xsl:for-each>
</xsl:variable>
```
I can print values from this new nodeset using:
```
<xsl:value-of select="$sortedNodeSet"/>
```
...but as soon as I try something like this:
```
<xsl:for-each select="$sortedNodeSet/*">
   <xsl:value-of select="@nodeName"/>
</xsl:for-each>
```
...I get Error parsing XSLT file.

Has anyone done this before in umbraco? If so, any clues how I can accomplish this?

Thanks in advance!
/Thomas K
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Thomas Kahn 602 posts 506 karma points

Nov 30, 2009 @ 12:16
0
Answering my own question: it seems like the result from the first for-each loop is not really a nodeset, but something called a tree fragment. In order to make it a nodeset you need to use exslt:node-set, like this:
```
<xsl:for-each select="exslt:node-set($sortedNodeSet)/*">
   <xsl:value-of select="@nodeName"/>
</xsl:for-each>
```
You will also need to add the namespace to the stylesheet. I added xmlns:exslt="http://exslt.org/common" in my stylesheet.

After having done this, it works like expected (so far)!

This is totally new to me so I'd love any input or improvements on this.

/Thomas K
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Chriztian Steinmeier 2800 posts 8791 karma points MVP 8x admin c-trib

Nov 30, 2009 @ 23:41

0

Hi Thomas,

Oh yes - that's why I said "If your data is already sorted by title", because this was the easy solution :-)

I'm a little uncertain if you've solved your problem using the node-set() function? (Incidentally, the function is already available in Umbraco as either msxml:node-set() or Exslt.ExsltCommon:node-set())

If you're still looking for a solution you should check out (i.e. google for) 'grouping' and 'muenchian' for the gory details... (or ask for an example)

/Chriztian

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Print to screen only when a value is different from the preceding value?