XSLT - Parameter value equals path to attribute, for query

[mrdancu]

Hi
I am very new to XSLT and have the following problem:
I would like to use a parameters value for the path to an attribute in my select query. For example:

I have an attribute named "pi" for the "date" element that sits in this path in my xml file:

visitors/visitor/date/@pi

so if I set the parameter:

<xsl:param name="myvar">date/@pi</xsl:param>

and create my select query to show each record with a date pi attribute with a value of 'Y':

<xsl:for-each select="visitors/visitor[$myvar = 'Y']">

it does not work as I was hoping???
I am probably thinking about things wrong, so if anyone could post any tips, that would be great.
Thanks,
Mat.

[Dormilich]

<xsl:param name="myvar">date/@pi</xsl:param>

$myvar is in this case a string (think of $myvar = 'date/@pi').

<xsl:param name="myvar" select="date/@pi"/>

will return a not-empty node/node-set if (and only if) the used xpath matches a node at the time of defining the parameter.

rule of thumb: <param> and <variable> are either empty, a string or a node-set. you cannot use them as part of an xpath-string like "/node()/$param/node()"

regards

[mrdancu]

Thanks for your reply. I think I understand!
I am currently passing the value of parameters from javascript using the following method:

xslProc.addParameter("myvar", "date/@pi");

This would add "date/@pi" to the value of $myvar, not to the select value of $myvar.

How would I achieve this?

[Dormilich]

I don't think that's correct, but I admit I don't use xslt via javascript.

I assume that the expression of $myvar is empty when you set the parameter.
add somewhere in your xsl: <xsl:value-of select="$myvar"/> to check for the content of $myvar.

furthermore, visitors/visitor[$myvar = 'Y'] will imho never work as intended, because you can't save an xpath in a variable (which you'd need for that, you only have string, number or node-set available).

I would like to use a parameters value for the path to an attribute in my select query.

to answer that clearly, you can't do that.


regards

PS: I wish I could save an xpath in a variable, would be very useful.....

[mrdancu]

Thanks again for the reply... I think you have confirmed what I thought, I can't pass an xpath query from javascript to an xslt file.
So I probably need to rethink what i am trying to acheive:

Basically I have a xml file with many visitor records (path: visitors/visitor) that have a date element with differing attributes.
Some will have an @pi1 = 'Y', some will have an @pi2 = 'Y', @pi3 = 'Y' etc etc etc up to @pi8.

What I would like to do is select the records based on whether they have a specific attribute or not.
I was trying to use javascript to achieve this with 1 xslt template and pass parameters to the xslt, but I may just have to use more than 1 template with a fixed query and vary the template used in the javascript.

If you have any other suggestions, that would be great.

Thanks again.
Mat.

[Dormilich]

you could try to get the parameter to hold the complete xpath.

// JS
xslProc.addParameter("myvar", "//visitor[date/@pi1 = 'Y']");
 
// XSL
<xsl:param name="myvar" select="//visitor[date/@pi1 = 'Y']"/>
// using
<xsl:for-each select="$myvar">
// code...
</xsl:for-each>

check with <value-of> what the variable holds.

regards

[jkmyoung]

If you treat the parameter as a name, then you could pass in a string. This would assume that values were either "Y" or "N".

xslProc.addParameter("myvar", "pi1");

<xsl:param name="myvar" select="'pi1'"/>
<xsl:for-each select="visitors/visitor[.//@*[local-name() = $myvar and .='Y']">

[mrdancu]

Thanks to both of you for you help. I seemed to have cracked it using the following code:

javascript:

xslProc.addParameter("myvar", "pi1");

XSLT:

<xsl:param name="myvar"/>  
<xsl:for-each select="visitors/visitor[date/@*[local-name() = $myvar]]">

If the date element has a @pi1, the record gets included!