Subject: Re: [xsl] How do I pass the mode as a string? From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Tue, 3 Mar 2020 16:32:01 -0000 |
The two things that come closest to polymorphism in XSLT (3.0) are (a) the template rule despatch mechanism, and (b) higher order functions. Both of these can be used to achieve dynamic selection of different functionality based on the input data encountered. Exactly how you would apply either mechanism in your scenario depends on having a deeper understanding of your specific transformation requirement. Modes weren't designed for this requirement and so it's hard to give you a forwards directions that doesn't start "If I were you, I wouldn't start from here". If you do have to start from here (i.e. you've got a collection of interchangeable modes and want to select one of them dynamically) then I'm afraid you're stuck with some kind of xsl:choose equivalent. Michael Kay Saxonica > On 3 Mar 2020, at 15:38, Kerry, Richard richard.kerry@xxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > Ok, > Thanks all for the explanations. I'll look at the alternatives. > If this was C++, which is what I use most of the time (XSL is infrequent, just when I want to manipulate some XML) I would use some kind of polymorphism to achieve this. I'd define a couple of one-line functions with the different variables, or calls, and pass the appropriate one to the outer function so they could be run on its results (somewhat garbled, abbreviated explanation, sorry). I'm not aware of anything in XSL that looks like polymorphism, but I would be interested to know if there was a construct that might be similar, or usable for cases like this one. > Granted I can't construct variable names dynamically, but I can have a number of variables existing simultaneously and select one and pass it around by address if I need to. I don't see an analogous construct in XSL, except to use choose/when to select a line of code based on an actual variable. > > I could send my examples if that would be best, but I think that would provide a lot of unnecessary code just to show a small bit of context. > What I am actually trying to do is to get a number of XML files processed. The files are in similar folders, called 'input' and 'output'. The files' names follow a couple of name patterns, acq_(\d{4}) and out_(\d{4}). There is identical code to scan through the folders and identify the files I want to process (and extract the numbers from the filenames). They are then passed to apply-templates with the different modes as mentioned. > So the file scanning, while not especially complicated, is not entirely trivial and I'd like to have it written just once. And then, because the contents of the files differs in structure, they are handled by different templates, with different modes. > > > > > > Richard Kerry > BNCS Engineer, SI SOL Telco & Media Vertical Practice > M: +44 (0)7812 325518 > 2nd Floor, MidCity Place, 71 High Holborn, London, WC1V 6EA > richard.kerry@xxxxxxxx <https://webmail.siemens-it-solutions.com/owa/redir.aspx?C=9fb20d019e3e4cb993 44d708709a3177&URL=mailto%3arichard.kerry%40atos.net> > > > > > > > > > > This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Atos group liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. > > > From: Michael Kay mike@xxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> > Sent: 03 March 2020 11:48 > To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx <xsl-list@xxxxxxxxxxxxxxxxxxxxxx> > Subject: Re: [xsl] How do I pass the mode as a string? > > Section B'6.6.2 in the XSLT 3.0 spec states: > > The xsl:apply-templates <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org %2FTR%2Fxslt-30%2F%23element-apply-templates&data=02%7C01%7Crichard.kerry%40a tos.net%7Cf54e291885cc4d7f604408d7bf68dcd8%7C33440fc6b7c7412cbb730e70b0198d5a %7C0%7C0%7C637188329424694875&sdata=eSQdcCjN4EO8jORS463GpcDU2L9K0dGwwHP6wU9zJ 3o%3D&reserved=0> element also has an optional mode attribute. The value of this attribute must be one of the following: > > an EQName <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org %2FTR%2Fxslt-30%2F%23dt-eqname&data=02%7C01%7Crichard.kerry%40atos.net%7Cf54e 291885cc4d7f604408d7bf68dcd8%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0%7C637 188329424694875&sdata=Fk%2FK%2FfJKIe1TdwQmwpizrP8xMug12fJUDBRGLfJG17g%3D&rese rved=0>, which is expanded as described in 5.1.1 Qualified Names <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org %2FTR%2Fxslt-30%2F%23qname&data=02%7C01%7Crichard.kerry%40atos.net%7Cf54e2918 85cc4d7f604408d7bf68dcd8%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0%7C6371883 29424704871&sdata=J9K12tJfdfAz4JxbQAcj9II%2FfTDTxabxPgUUSo5aHv0%3D&reserved=0> to define the name of a mode > the token #default, to indicate that the default mode for the stylesheet module <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org %2FTR%2Fxslt-30%2F%23dt-stylesheet-module&data=02%7C01%7Crichard.kerry%40atos .net%7Cf54e291885cc4d7f604408d7bf68dcd8%7C33440fc6b7c7412cbb730e70b0198d5a%7C 0%7C0%7C637188329424704871&sdata=a6iW12SrGH06RlMcl2h9b8dJI3REzfkYOrO5Au8g9z4% 3D&reserved=0> is to be used > the token #unnamed, to indicate that the unnamed mode <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org %2FTR%2Fxslt-30%2F%23dt-unnamed-mode&data=02%7C01%7Crichard.kerry%40atos.net% 7Cf54e291885cc4d7f604408d7bf68dcd8%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0 %7C637188329424714867&sdata=i6lQizANc28QMchUjq6CdLldwmM57L1PNleISc%2F%2BDHo%3 D&reserved=0> is to be used > the token #current, to indicate that the current mode <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.w3.org %2FTR%2Fxslt-30%2F%23dt-current-mode&data=02%7C01%7Crichard.kerry%40atos.net% 7Cf54e291885cc4d7f604408d7bf68dcd8%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0 %7C637188329424714867&sdata=%2FSSYYInob%2BrZ3Jj5CQK2mqWdJgtpzkoGFsBxM%2FDihKs %3D&reserved=0> is to be used > It does not allow an expression, and it does not allow an attribute value template. > > It's similar to trying to refer to a variable by name: you can't construct variable names dynamically either, however much you feel it would make your life easier. > > You haven't described your problem so it's difficult to suggest a different approach to solving it. Higher-order functions might be the right way. > > Michael Kay > Saxonica > > XSL-List info and archive <http://www.mulberrytech.com/xsl/xsl-list> > EasyUnsubscribe <http://lists.mulberrytech.com/unsub/xsl-list/293509> (by email <>)
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