filtering xml with xslt

[tonyamak]

I am dabbling with xml and trying to learn to harness its power...
( should have been doing this years ago, admittedly!)

my xml file is structured like so...


<clientxyz>
<Events>
<EventListing ID="5829" Title="Excavating Egyptian Archaeology"></
EventListing>
<EventListing ID="7824" Title="Ladies Day on the Lake"></
EventListing>
<EventListing ID="7825" Title="A Taste of Newberry"></EventListing>
<EventListing ID="7826" Title="Brew At The Zoo"></EventListing>
<EventListing ID="7827" Title="Veterans Day"></EventListing>
</Events>
<EventSearch>
<FindEventID eID="5290">5290</FindEventID>
</EventSearch>
</clientxyz>


What Im trying to figure out in terms of XSLT filtering (using xsl:if,
if guess(???)) is how can I have a page loop through the <Events>
node and look for the 'match' of the <FindEventID>'s eID attribute?
(( or would this be easer if I had an <eID> node within the
<FindEventID> node?


basically Im looking for an example of what the structure of the xsl
if statement / line would look like.

 

[k5tm]

Some basic tutorials might help: XSLT Xpath

In general, one would not loop looking for something. The concept of looping comes from your procedural programming experience. While XSL has an xsl:for-each processing instruction, you are really declaring how to treat each node of a nodeset.

Instead, one would use an XPath predicate, much like you would use a WHERE clause in SQL rather than loop through all the rows in a table looking for the right row.

The form of an XPath expression for the requirement might look something like this:

clientxyz/Events/EventListing[@ID = //EventSearch/FindEventID]

This is evaluated as:
[ul][li]Find the nodeset of EventListing nodes subordinate to a Events node which in turn is subordinate to[/li][li]a clientxyz node, where[/li][li]the value of the ID attribute in the EventListing node(s) equals[/li][li]the value of a FindEventID node which is subordinate to [/li][li]an EventSearch node which is anywhere in the document[/li][/ul]
The expression inside the square brackets [] is the predicate which limits the set of EventListing nodes that are returned.

Tom Morrison

http://www.liant.com

 

[tonyamak]

ahhhh... I think I get it.

Thanks.

Question so would the xsl 'statement' be something like:

<xsl:when clientxyz/Events/EventListing[@ID = //EventSearch/FindEventID]>

... whatver I want to show when a match is found for id...

</xsl:when>

 

[tsuji]

[0] Your EventSearch has no match to EventListing in the example. You should at least add some which do have matches to see more clearly the outcome.

[1] When you conceive the approach involving xsl:when at all, you are using a pull approach (more closely analoguous to procedureal). This may be a slightly more advanced viewpoint than presently you need to see the thing. Besides, your xsl:when syntax is not correct.

[2] The intriguing thing is that the = in the predicate is a kind of called general comparison. It is not two-value logic. a=b maybe true, at the same time a!=b maybe true as well, (for some nodes of EventListing). But again this is a more difficult point.

[3] To help you see the point made by k5tm, this is a push kind of xslt using the exact one line of xpath.
[tt]
<?xml version="1.0" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="

http://www.w3.org/1999/XSL/Transform">

<xslutput method="text" />
<xsl:template match="/">
<xsl:apply-templates select="clientxyz/Events/EventListing" />
</xsl:template>
[blue]<xsl:template match="clientxyz/Events/EventListing[@ID = //EventSearch/FindEventID]">[/blue]
<xsl:value-of select="concat(@ID,':','&#x0d;&#x0a;')" />
<xsl:value-of select="concat('&#09;',@Title,'&#x0d;&#x0a;')" />
</xsl:template>
</xsl:stylesheet>
[/tt]
[3.1] There are equally valid substitutions with more or less clarity to the blue line above, depending of how you look at the problem.
[tt]
<xsl:template match="clientxyz/Events/EventListing[@ID = ../../EventSearch/FindEventID]">
<!-- since eID and the text are the same (but eID may be less accidental -->
<xsl:template match="clientxyz/Events/EventListing[@ID = ../../EventSearch/FindEventID/@eID]">
<!-- or -->
<xsl:template match="clientxyz/Events/EventListing[@ID = //EventSearch/FindEventID/@eID]">
[/tt]
[4] You can also experiment by looking at what do get in the special kind of "not equal" (!=) behaviour and may find it perplexed, as explained in [2].
[tt]
<xsl:template match="clientxyz/Events/EventListing[@ID [highlight]![/highlight]= ../../EventSearch/FindEventID/@eID]">
[/tt]