subclassing in XSLT

[Andy Fish]

Hi,

I'm trying to achieve something like subclassing in XSLT, by which I mean
that I have stylesheet A and I want to make a more specialised "subclass"
called stylesheet B. which inherits most of the functions but overrides some
templates.

the closest I can think of getting is to write template B including template
A, and then put templates in B with the same "match" clause but with a
higher priority than A. Unfortunately, a key feature would be to invoke the
superclass method as part of the overridden method, and I can't see any way
to do this.

TIA for Any ideas

Andy

 

[Martin Honnen]

Andy Fish wrote:

the closest I can think of getting is to write template B including template
A, and then put templates in B with the same "match" clause but with a
higher priority than A. Unfortunately, a key feature would be to invoke the
superclass method as part of the overridden method, and I can't see any way
to do this.

Doesn't
<xsl:apply-imports />
do what you want?

 

[Patrick TJ McPhee]

% the closest I can think of getting is to write template B including template
% A, and then put templates in B with the same "match" clause but with a
% higher priority than A. Unfortunately, a key feature would be to invoke the

xsl:import does this implicitly.


% superclass method as part of the overridden method, and I can't see any way
% to do this.

Once you've used xsl:import, you can invoke the template from the imported
stylesheet using xsl:apply-imports.

<!-- stylesheet A.xsl -->
<xsl:stylesheet version='1.0'
xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>

<xslutput method='text'/>

<xsl:template match='A'>
<xsl:text>standard processing of A.</xsl:text>
</xsl:template>
</xsl:stylesheet>


<!-- stylesheet B.xsl -->
<xsl:stylesheet version='1.0'
xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>

<!-- this must come first! -->
<xsl:import href='A.xsl'/>

<xsl:template match='A'>
<xsl:text>Specialised processing of A, followed by </xsl:text>
<xsl:apply-imports/>
</xsl:template>
</xsl:stylesheet>

<!-- A.xml -->
<A/>

of course in the real world I would use names like x.xsl and y.xsl.
Anyway, if you process A.xml using A.xsl, you get this output

standard processing of A.

while if you process A.xml using B.xsl, you get this

Specialised processing of A, followed by standard processing of A.

 

[Andy Fish]

xsl:import does this implicitly.

D'oh!

Thanks guys - I hadn't noticed that one before.

 

[Dimitre Novatchev [MVP]]

Just a note that in XSLT 1.0 xsl:apply-imports cannot be passed any
parameters.

There are also some nasty surprises with import precedence -- e.g. see what
Jeni Tennison had to say at:

http://www.biglist.com/lists/xsl-list/archives/200102/msg01135.html

I guess the latter remains true in XSLT 2.0, too.

Cheers,

Dimitre Novatchev.

 

[David Carlisle]

I guess the latter remains true in XSLT 2.0, too.

yes although in 2 you can use next-match rather than apply-imports (with
or without using xsl:import) this has rather different behaviour on edge
cases.

David