xsl-list
[Top] [All Lists]

Re: top level params and xsl:attribute magic?

2003-01-18 00:34:56
Another way to completely avoid both having to use xx:evaluate() or an
external API:

Instead of using the XPath expression to a node as its unique id, use
the pair: 

(count(ancestor::node()), count(preceding::node()) )

This means that you will be passing as parameter a pair of numbers,
e.g.:

3,15

Then you can get these two numbers in two variables and find your node
with the following XPath expression:

//node()[count(ancestor::node()) = $v1 
       and 
         count(preceding::node()) = $v2
         ]

Or you could define a key, so that the node(s) will be found faster.



=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL



--- Dimitre Novatchev <dnovatchev(_at_)yahoo(_dot_)com> wrote:
First, I would stroongly recommend *not* to use any xx:evaluate
function.

As anyway you are passing the XPath expression through a global
xsl:param (which is done outside of XSLT processing, using some kind
of
API), it would be much better to set the value of the "select"
attribute of this particular xsl:param (again through the API (most
probably XML DOM)) to the string/XPath-expression.

This is both simple and efficient, it completely eliminates your
current problem.

Compare to this (which doesn't work): (2)
   <xsl:param name="StartNode">
         <xsl:attribute name="select">
           <xsl:value-of select="dyn:evaluate($StartPointStr)"/>
         </xsl:attribute>
   </xsl:param>

(1) works and (2) doesn't work.

In the snippet above you're specifying the value of the "select"
attribute to the *string* value of the *first* node in the node-set
returned by dyn:eveluate().

This, of course, is completely different to setting the "select"
attribute to the node-set.

Once again, the best way in your situation is to forget about
extension
functions and to set the "select" attribute totally from outside and
just before the start of the transformation.

This is the way the XPath Visualiser (both for IE and Mozilla) works
--
do have a look at its code.


=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL



"S Woodside" <sbwoodside(_at_)yahoo(_dot_)com> wrote in message
news:F2CC80BE-2AA0-11D7-8385-000393414368(_at_)yahoo(_dot_)com(_dot_)(_dot_)(_dot_)
I'm beginning to think that XSLT is a bit like magic. If you think
the 
right way, and use the right magic incantation, it works like a
charm. 
If you don't, no cigar.

I have this top-level param to grab a param from http:
   <xsl:param name="StartPointStr">.</xsl:param>

The param StartPointStr is an Xpath string. Next I have this (which

works) (1)
   <xsl:param name="StartNode"
select="dyn:evaluate($StartPointStr)"/>

Compare to this (which doesn't work): (2)
   <xsl:param name="StartNode">
         <xsl:attribute name="select">
           <xsl:value-of select="dyn:evaluate($StartPointStr)"/>
         </xsl:attribute>
   </xsl:param>

(1) works and (2) doesn't work. With two, I get nothing, empty node

set. They should be equivalent!

OK, wait, I see in the spec "The xsl:attribute element can be used
to

add attributes to result elements" ... so this must be an illegal
use

of xsl:attribute. But LibXSLT doesn't complain ... maybe this is
just
a 
case of inadequate error detection and reporting the in the 
implementation (I used to see that very often in C++ compilers...)

simon

---
www.simonwoodside.com


 XSL-List info and archive: 
http://www.mulberrytech.com/xsl/xsl-list


__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com



__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list