Hi,
Extending on Jenny Tennison example of using document example to compare
file elements
I ran into some interesting behavior regarding variables as I tried to compare
elements in the same position in 2 files.
Please see the examples and questions below
Example XML Files:
File Containing references to other Files
<files>
<file href="file1.xml" />
<file href="file2.xml" />
</files>
file1.xml :
<file>
<Products>
<Product name="1"/>
<Product name="2"/>
<Product name="3"/>
</Products>
</file>
file2.xml :
<file>
<Products>
<Product name="1"/>
<Product name="20"/>
<Product name="3"/>
</Products>
</file>
In the stylesheet the following global variables are declared:
<xsl:variable name="file1"
select="document(/files/file[1]/@href, /)" />
<xsl:variable name="file2"
select="document(/files/file[2]/@href, /)" />
Later inside template matches or for-each loops I try to use these
variables to compare elements by position(product elements). I am unable to do
a value-of on them.
Example:
1) Inside a template match on *, or $file1//Product the following
strangeness occurs:
<xsl:value-of select="$file1//Product[1]/@name" /> prints the name of the
product
but <xsl:value-of select="$file1//Product[2]/@name"/> does not print
anything.
It seems test clauses are able to access the values in the variables but
value-of can't.
Example:
2) Inside a similar template or foreach
The following test is true when the second product in file2 is different.
It seems the test in the match is true although the Product[1] in both files
are the same. It is somehow matching the second products in the 2 files. Even
so if I try to print the second product name attribute it does not work.
<xsl:when test="$file1//Product[1]/@name != $file2//Product[1]/@name">
CHANGE DETECTED
<xsl:if test="$file2//Product[1]/@name='20'">20</xsl:if>
<!-- the test can access the second files second product-->
<xsl:value-of select="$file2//Product[2]/@name" />
<!-- the value of prints nothing proving it cannot access the second
file's second product-->
</xsl:when>
If Product[1] is somehow iterating through the Product nodes that is cool.
But why can't I access the value of attributes in a value-of statement when
xsl:when or xsl:if test clauses can?
xsl:value of can access elements by position if the variable points to the
specific element in the file
Example:
3) If a variable pointing to the product node is created then it is
possible to access the Product attributes using positions. It seems positions
only work on the element stored in the variable and not on subelements of
elements in a variable
The following works:
<xsl:variable name="product1" select="document(/files/file[2]/@href,
/)//Product" />
<xsl:value-of select="$product1[2]//@name" />
<!-- the second product in file can be accessed this way-->
but I don't understand why. It is in convenient to have to create many
variables for a file to access each element that needs to be accessed by
position.
If you can explain why these things work the way they do please let me
know or if are these idiosyncrasies are bugs?
Also I have tried this in xalan and saxon and get the same behavior, so I
assume this is not a bug but a lack of understanding on my part.
thanks
DS
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