What are the differences between call-template and apply-templates in XSL

Question

I am new in XSLT so I m little bit confused about the two tags     lt xsl apply-templates name  nodes  gt    and   lt xsl call-template select  nodes  gt     So can you list out the difference between them

User · Answer

The functionality is indeed similar  apart from the calling semantics  where call-template requires a name attribute and a corresponding names template    However  the parser will not execute the same way   From MSDN      Unlike  lt xsl apply-templates gt    lt xsl call-template gt  does not change the current node or the current node-list

User · Answer

lt xsl call-template gt  is a close equivalent to calling a function in a traditional programming language    You can define functions in XSLT  like this simple one that outputs a string    lt xsl template name  dosomething  gt     lt xsl text gt A function that does something lt  xsl text gt   lt  xsl template gt    This function can be called via  lt xsl call-template name  dosomething  gt     lt xsl apply-templates gt  is a little different and in it is the real power of XSLT  It takes any number of XML nodes  whatever you define in the select attribute   iterates them  this is important  apply-templates works like a loop   and finds matching templates for them    lt  -- sample XML snippet -- gt   lt xml gt     lt foo   gt  lt bar   gt  lt baz   gt   lt  xml gt    lt  -- sample XSLT snippet -- gt   lt xsl template match  xml  gt     lt xsl apply-templates select       gt   lt  -- three nodes selected here -- gt   lt  xsl template gt    lt xsl template match  foo  gt   lt  -- will be called once -- gt     lt xsl text gt foo element encountered lt  xsl text gt   lt  xsl template gt    lt xsl template match     gt   lt  -- will be called twice -- gt     lt xsl text gt other element countered lt  xsl text gt   lt  xsl template gt    This way you give up a little control to the XSLT processor - not you decide where the program flow goes  but the processor does by finding the most appropriate match for the node it s currently processing    If multiple templates can match a node  the one with the more specific match expression wins  If more than one matching template with the same specificity exist  the one declared last wins   You can concentrate more on developing templates and need less time to do  plumbing   Your programs will become more powerful and modularized  less deeply nested and faster  as XSLT processors are optimized for template matching    A concept to understand with XSLT is that of the  current node   With  lt xsl apply-templates gt  the current node moves on with every iteration  whereas  lt xsl call-template gt  does not change the current node  I e  the   within a called template refers to the same node as the   in the calling template  This is not the case with apply-templates    This is the basic difference  There are some other aspects of templates that affect their behavior  Their mode and priority  the fact that templates can have both a name and a match  It also has an impact whether the template has been imported   lt xsl import gt   or not  These are advanced uses and you can deal with them when you get there

User · Answer

xsl apply-templates is usually  but not necessarily  used to process all or a subset of children of the current node with all applicable templates  This supports the recursiveness of XSLT application which is matching the  possible  recursiveness of the processed XML   xsl call-template on the other hand is much more like a normal function call  You execute exactly one  named  template  usually with one or more parameters   So I use xsl apply-templates if I want to intercept the processing of an interesting node and  usually  inject something into the output stream  A typical  simplified  example would be   lt xsl template match  foo  gt     lt bar gt       lt xsl apply-templates  gt     lt  bar gt   lt  xsl template gt    whereas with xsl call-template I typically solve problems like adding the text of some subnodes together  transforming select nodesets into text or other nodesets and the like - anything you would write a specialized  reusable function for   Edit   As an additional remark to your specific question text     lt xsl call-template name  nodes   gt     This calls a template which is named  nodes         lt xsl template name  nodes  gt     lt  xsl template gt    This is a different semantic than    lt xsl apply-templates select  nodes   gt       which applies all templates to all children of your current XML node whose name is  nodes

User · Answer

To add to the good answer by  Tomalak   Here are some unmentioned and important differences    xsl apply-templates is much richer and deeper than xsl call-templates and even from  xsl for-each  simply because we don t know what code will be applied on the nodes of the selection -- in the general case this code will be different for different nodes of the node-list   The code that will be applied can be written way after the xsl apply templates was written and by people that do not know the original author    The FXSL library s implementation of higher-order functions  HOF  in XSLT wouldn t be possible if XSLT didn t have the  lt xsl apply-templates gt  instruction   Summary  Templates and the  lt xsl apply-templates gt  instruction is how XSLT implements and deals with polymorphism   Reference  See this whole thread  http   www biglist com lists lists mulberrytech com xsl-list archives 200411 msg00546 html

[xslt] What are the differences between 'call-template' and 'apply-templates' in XSL?

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