Re: [xsl] Using keys in templates

["M. David Peterson" <m.david@xxxxxxxxxx>]

Jeni Tennison wrote:

> <xsl:template match="module">
>   <xsl:apply-templates
>     select="dist[generate-id(.) =
>                  generate-id(key('dists', @name))]" />
> </xsl:template>
>
> <xsl:template match="dist">
>   <!-- this template only processed for the first dist element with
>        each particular name -->
>   ...
> </xsl:template>

The other benefit that comes with Jeni's approach is the ability to use 
variables within the value of the select attribute of <xsl:apply-templates...>, 
something that is not legal in the match attribute of <xsl:template...>.  As 
Jeni pointed out...

"Locating which template to use to process a node takes time, so you
should try to apply templates to as small a set as possible rather
than trying to find a template for every node, but only doing
something with some of them."

... this method ensures that only those elements which evaluate to true are sent 
to be matched to a template.  In your original post you were using the value of 
a variable as the value for the key function to match against the list of 
elements selected using <xsl:key...>.  As both Jeni and David indirectly pointed 
out the creation of the "dist" variable wasn't necessary in your particular case 
as the dist element was still the context element when you used the conditional 
<xsl:if...> element and as such "@name" referenced the same value that was being 
held in the "dist" variable.  But if this wasnt the case (you had implemented a 
for-each loop for example) then using the value of this variable within the key 
function would have made sense and would have allowed you the ability to further 
qualify what elements should be selected and matched to a template.

Hope you find this helpful!

Best regards,

<M:D/>