XSL dynamic schema

Question

I can't find a reason why the following does not work.

If I have a document that looks like

<mydocroot>
<request>
   <key>Ham</key>
</request>
<node>
   <data alias='Ham' id='27'>Some value</data>
   <data alias='Eggs' id='14'>Greenish</data>
   <data alias='Condiment' id='32'>Salt and pepper</data>
   ...
</node>
</mydocroot>

and an xsl template that looks like

<xsl:template match="/">
    <xsl:value-of select="/mydocroot/node/data[@alias=string(/mydocroot/request/key)]" />
</xsl:template>

prints nothing.

<xsl:template match="/">
    <xsl:value-of select="/mydocroot/node/data[@alias='Ham']" />
</xsl:template>

prints "Some value" as expected.

What am I doing wrong?

Thanks!

Edit:

I'm actually not 100% positive what the underlying document I'm working with looks like, but I do know that, to continue with this example,

<xsl:value-of select="/mydocroot/request/key" /> <!-- prints "Ham" -->

works.

Should I be able to match an attribute value to a node value?

Answer 1

If you start an XPath expression using a "/", it indicates that you are starting from the root node of the document, but the root element is "mydocroot", so you need to include that in your XPath.

<xsl:value-of select="/mydocroot/node/data[@alias=string(/mydocroot/request/key)]" />

Answer 2

So I got the following to work, but it seems hackish:

<xsl:template match="/">
    <xsl:variable name="aliasval"><xsl:value-of select="string(/mydocroot/request/key)" /></xslvariable>
    <xsl:value-of select="/myrootdoc/node/data[@alias=$aliasval]" />
</xsl:template>

Should I be required to create a variable just for this? I'm probably bumping up against my knowledge of XSLT here.

Answer 3

"Should I be able to match an attribute value to a node value?"

Definitively yes. An attribute value is a string, and when comparing against a string, XSLT coerces the other operand to a string automatically. No need to call string() explicitly. This works for me (and it should work for you as well):

<xsl:value-of select="/mydocroot/node/data[@alias = /mydocroot/request/key]" />
<!-- prints "Some value" -->

Better, because more explicit (/mydocroot/request/key could select more than one node!):

<xsl:value-of select="/mydocroot/node/data[@alias = /mydocroot/request/key[1]]" />

In these siutations, an <xsl:key> also would come in handy:

<xsl:key name="kDataByAlias" match="node/data" use="@alias" />

<!-- later... -->

<xsl:value-of select="key('kDataByAlias', /mydocroot/request/key[1])" />