RE: [xsl] conditional template matching & failure

["Michael Kay" <michael dot h dot kay at ntlworld dot com>]

> Generally, I have an XML file with student schedule 
> information in it and I want to print each class out when 
> given a specific student & term. A student may not exist in 
> the XML file, however, for whatever reason.
> 
> 
> > if student & term found
>    > print schedule
> > else
>   > give a "not found" msg
> 
> ---------
> Problems:
> ---------
> 
> 1. Without using xsl:if or :choose, I can't stop a failed 
> template match from dumping the entire data

If your template rule isn't selected, the built-in template rule is
selected, and this does an implicit <xsl:apply-templates/>. If you want
it to do nothing, override it like this:

<xsl:template match="schedule"/>

And by the way, you don't need "//" at the start of a match pattern.
> 
>    Example:
> 	<xsl:template match="//schedule[@username=$thisUser]">
>         ...
>         </xsl:template>
> 
>    Results: prints out entire XML if $thisUser is not found
> 
> 
> 2. Using xsl:if and :choose doesn't traverse me down the tree 
> to the elements I want to print, so I'm writing long (and 
> expensive) XPaths on the subsequent condition
> 
>    Example:
> 	<xsl:for-each 
> select="//schedule[@username=$thisUser]/semester[season=$thisS
> eason and year=$thisYear]/course">
> 	  ...
> 	</xsl:for-each>
> 
>    Results: long, slow, inefficient XPath - should just be 
> able to say "for-each select='course'"

You can write a relative path expression if you get the context right.
The context node is a <schedule> element, so the relative path you need
is 

select="semester[season=$thisSeason and year=$thisYear]/course"
> 
> 
> 3. I can't use a template match with a VariableReference 
> (student name), but I can't create a separate template for 
> every case either (too many
> students)
> 
>    Example:
> 	<xsl:apply-templates 
> select="//schedule[@username=$thisUser]/semester"/>
> 	  ...
> 	<xsl:template match="//schedule[@username=$thisUser]/semester">
> 	  ...
> 	</xsl:template>
>

Try using modes:

<xsl:apply-templates 
   select="//schedule[@username=$thisUser]/semester" 
   mode="thisUser"/>

<xsl:template match="schedule" mode="thisUser">...


Michael Kay
Software AG
home: Michael.H.Kay@ntlworld.com
work: Michael.Kay@softwareag.com 
 
>    Results: invalid XSL
> 
> ---------------------
> schedule.xml
> ---------------------
> <schedules>
> 
>   <schedule username="tommy">
> 
>     <semester>
>       <season>fall</season>
>       <year>2002</year>
> 
>       <course>
>         <title>Calc 1</title>
>         <desc>...</desc>
>       </course>
> 
>       <course>
>         <title>Gym</title>
>         <desc>...</desc>
>       </course>
> 
>     </semester>
> 
>   </schedule>
> 
> </schedules>
> --------------------
> - can be 1 to many <schedule>
> - can be 1 to many <semester>
> - can be 1 to many <course>
> --------------------
> 
> I want to template match to the level of <semester> so I'm 
> only processing at that level to print out the course info 
> and if the <schedule> username attribute is not found, it 
> returns "not found."
> 
> I tried doing something like:
> 
> <xsl:template match="schedule[@username=$thisUser]">
> 
>   <table>
> 
>   <xs:apply-templates select="semester[season=$thisSeason and 
> year=$thisYear]"/>
> 
>   </table>
> 
> </xsl:template>
> 
> <xsl:template match="semester[season=$thisSeason and year=$thisYear]">
>    <xsl:for-each select="course">
> 
>      <tr><td><xsl:value-of select="title"/></td></tr>
> 
>    </xsl:for-each>
> </xsl:template>
> 
> ------
> This obviously fails because you can't have a 
> VariableReference in the template match, but this is the gist 
> of what I'm trying to accomplish.
> 
> Any and all help is appreciated as I try to get my feet wet.
> 
> 
> Regards,
> _ryan
> 
> 
>  XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list
> 


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