Functions with multiple optional parameters

baseliner · December 7th, 2009, 04:34 PM

I have a function that has two parameters.. I'd like to be able to call it with either one or both parameters.. is it possible to do this in XSLT 2.0 without having to resort to empty arguments in the function call? For example:

Code:

<xsl:function name="lbs:myfn" as="xs:string">
		<xsl:param name="param1" as="xs:string"/>
		<xsl:param name="param2" as="xs:string"/>
 <!-- some logic here -->
</xsl:function>

I'd like to be able to call the function with one or both of param1 and param2.. I see that there's an optional attribute for param but not sure how the function should be invoked if I do specify both the above as optional and want to call it with just one param.. thanks!

samjudson · December 7th, 2009, 04:38 PM

I believe you can simply specify the parameter with a default value:

<xsl:param name="param1" as="xs:string" select="''"/>

Edit: Sorry, its a function you're talking about. Can't remember, let me look it up.

samjudson · December 7th, 2009, 04:42 PM

Sorry, optional parameters for functions are not allowed:

http://www.w3.org/TR/xslt20/#stylesheet-functions

baseliner · December 7th, 2009, 04:42 PM

So when I invoke the function, I still need to pass 2 arguments as follows (assuming I want to invoke with one real argument for param2):

lbs:myfn('','blah')

If so, this would be quite cumbersome when the number of parameters is large, wouldn't it?

mhkay · December 7th, 2009, 04:43 PM

You can write another function with the same name that only has one parameter, which calls your 2-param version supplying the default value for the second parameter. But you can't make both arguments optional this way, it would be ambiguous.

baseliner · December 7th, 2009, 04:47 PM

Right, I implemented that for another case but that would only work if exactly one parameter was optional.. so it appears for the multiple optional parameters case, I need to write multiple functions... :(

mhkay · December 7th, 2009, 05:31 PM

>If so, this would be quite cumbersome when the number of parameters is large, wouldn't it?

If the number of arguments is more than 3 or 4 then there's probably something wrong with your design. Consider passing a structured XML object as a single argument.