Re: Apply Templates, when to use which? how do templat
> How does one get rid of default templates? just define templates that do something else. for example if you do (and I often do) <xsl:template match="*"> <xsl:message> Unexpected element: <xsl:value-of select="name()"/> </xsl:message> </xsl:template> Then the default behaviour if templates are applied to an element for which a more specific template has been defined is to make a warning message and not process the eelement or its descendents, instead of the original default which is to silently ignore the element but process its children. > What's the behaviour of xslt 2.0 in this regards? xslt2 allows you to start at a named template (that is starting with an implicit call to xsl:call-template, rather than an implict call to xsl:apply-templates select="/") > but it appears that using call-template can > achieve what the others achieve plus the use of parameters. No, on both counts, xsl:call-template can not replicate apply-template functionality (unless you actually try to implement xslt using xslt as the implementation language. And both apply-templates and call-template have the same functionality with respect to parameter passing (with the same syntax as well). > Also, are there any efficiency implications with each of these ? > <apply-templates /> > > <apply-templates select="xyz" /> > > <apply-templates select="xyz" mode="foo" /> as I said earlier <apply-templates />is <apply-templates select="node()"/> so the difference between the first two is not a mater of efficiency as requirements. It's like asking if calculating 1+1 is more efficient than calculating cos(x)^2 it may be but if it's not the answer you need that's not very usieful information. Clearly depending on the complaecity of you real XPath expression ("xyz" here) this may take an arbitrary amount of time to calculate teh set of nodes taht are going to be evaluated, but if that is the set you need, then quickly evaluating teh set of all child nodes with the first form isn't going to help. the third form is just as efficient or inefficient as the second, the process the xslt engine goes through is the same but using teh templates marked with mode="foo" rather than those without a mode attribute as happens in the first two cases. > > <call-template name="bar" /> This is completely different to apply-templates so you can't really compare it for efficiency. There are several good sxslt tutorials on the web, and it's well worth just experimenting with some small stylesheets to see the difference. As a start consider a strylesheet that's just doing name changing, that is copy th einput to the output but change <img> to <object> using apply-templates you take an identity transform and add one extra template to do teh chaneg specified <xsl:template match="img"> <object> <xsl:apply-templates/> </object> </xsl:template> and that's all you need. It's virtually impossible to do that kind of transform using call-template unless you code an explicit recursive walk over the input tree (as you would have to do in XQuery for example, which is essentially XSLT without xsl:apply-templates). David ________________________________________________________________________ The Numerical Algorithms Group Ltd is a company registered in England and Wales with company number 1249803. The registered office is: Wilkinson House, Jordan Hill Road, Oxford OX2 8DR, United Kingdom. This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. ________________________________________________________________________
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