Provided by: libconfig-model-perl_2.133-1_all bug


       Config::Model::Warper - Warp tree properties


       version 2.133


        # internal class


       Depending on the value of a warp master (In fact a Config::Model::Value or a
       Config::Model::CheckList object), this class changes the properties of a node
       (Config::Model::WarpedNode), a hash (Config::Model::HashId), a list
       (Config::Model::ListId), a checklist (Config::Model::CheckList) or another value.

Warper and warped

       Warping an object means that the properties of the object is changed depending on the
       value of another object.

       The changed object is referred as the warped object.

       The other object that holds the important value is referred as the warp master or the
       warper object.

       You can also set up several warp master for one warped object. This means that the
       properties of the warped object is changed according to a combination of values of the
       warp masters.

Warp arguments

       Warp arguments are passed in a hash ref whose keys are "follow" and and "rules":

   Warp follow argument
       Grab string leading to the "Config::Model::Value" or Config::Model::CheckList warp master.

        follow => '! tree_macro'

       In case of several warp master, "follow" is set to an array ref of several grab string:

        follow => [ '! macro1', '- macro2' ]

       You can also use named parameters:

        follow => { m1 => '! macro1', m2 => '- macro2' }

       Note: By design "follow" argument of warper module is a plain path to keep warp mechanism
       (relatively) simple. "follow" argument of Config::Model::ValueComputer has more features
       and is documented there

   Warp rules argument
       String, hash ref or array ref that specify the warped object property changes.  These
       rules specifies the actual property changes for the warped object depending on the
       value(s) of the warp master(s).

       E.g. for a simple case (rules is a hash ref) :

        follow => '! macro1' ,
        rules => { A => { <effect when macro1 is A> },
                   B => { <effect when macro1 is B> }

       In case of similar effects, you can use named parameters and a boolean expression to
       specify the effect. The first match is applied. In this case, rules is a list ref:

         follow => { m => '! macro1' } ,
         rules => [ '$m eq "A"'               => { <effect for macro1 == A> },
                    '$m eq "B" or $m eq"C "'  => { <effect for macro1 == B|C > }

       In case of several warp masters, "follow" must use named parameters, and rules must use
       boolean expression:

        follow => { m1 => '! macro1', m2 => '- macro2' } ,
        rules => [
                  '$m1 eq "A" && $m2 eq "C"' => { <effect for A C> },
                  '$m1 eq "A" && $m2 eq "D"' => { <effect for A D> },
                  '$m1 eq "B" && $m2 eq "C"' => { <effect for B C> },
                  '$m1 eq "B" && $m2 eq "D"' => { <effect for B D> },

       Of course some combinations of warp master values can have the same effect:

        follow => { m1 => '! macro1', m2 => '- macro2' } ,
        rules => [
                  '$m1 eq "A" && $m2 eq "C"' => { <effect X> },
                  '$m1 eq "A" && $m2 eq "D"' => { <effect Y> },
                  '$m1 eq "B" && $m2 eq "C"' => { <effect Y> },
                  '$m1 eq "B" && $m2 eq "D"' => { <effect Y> },

       In this case, you can use different boolean expression to save typing:

        follow => { m1 => '! macro1', m2 => '- macro2' } ,
        rules => [
                  '$m1 eq "A" && $m2 eq "C"' => { <effect X> },
                  '$m1 eq "A" && $m2 eq "D"' => { <effect Y> },
                  '$m1 eq "B" && ( $m2 eq "C" or $m2 eq "D") ' => { <effect Y> },

       Note that the boolean expression is sanitized and used in a Perl eval, so you can use most
       Perl syntax and regular expressions.

       Functions (like &foo) are called like "$self->foo" before evaluation of the boolean

       The rules must be declared with a slightly different way when a check_list is used as a
       warp master: a check_list has not a simple value. The rule must check whether a value is
       checked or not amongs all the possible items of a check list.

       For example, let's say that $cl in the rule below point to a check list whose items are
       "A" and "B". The rule must verify if the item is set or not:

         rules => [
              '$cl.is_set(A)' =>  { <effect when A is set> },
              '$cl.is_set(B)' =>  { <effect when B is set> },
              # can be combined
              '$cl.is_set(B) and $cl.is_set(A)' =>  { <effect when A and B are set> },

       With this feature, you can control with a check list whether some element must be shown or
       not (assuming "FooClass" and "BarClass" classes are declared):

           element => [
               # warp master
               my_check_list => {
                   type       => 'check_list',
                   choice     => ['has_foo','has_bar']
               # controlled element that show up only when has_foo is set
               foo => {
                   type => 'warped_node',
                   level => 'hidden',
                   config_class_name => 'FooClass',
                   follow => {
                       selected => '- my_check_list'
                   'rules' => [
                       '$selected.is_set(has_foo)' => {
                           level => 'normal'
               # controlled element that show up only when has_bar is set
               bar => {
                   type => 'warped_node',
                   level => 'hidden',
                   config_class_name => 'BarClass',
                   follow => {
                       selected => '- my_check_list'
                   'rules' => [
                       '$selected.is_set(has_bar)' => {
                           level => 'normal'


       This method returns a string describing:

       ·   The location(s) of the warp master

       ·   The current value(s) of the warp master(s)

       ·   The other values accepted by the warp master that can be tried (if the warp master is
           an enumerated type)

How does this work ?

           ·   When a warped object is created, the constructor registers to the warp masters.
               The warp master are found by using the special string passed to the "follow"
               parameter. As explained in grab method, the string provides the location of the
               warp master in the configuration tree using a symbolic form.

           ·   Then the warped object retrieve the value(s) of the warp master(s)

           ·   Then the warped object warps itself using the above value(s). Depending on these
               value(s), the properties of the warped object are modified.

       Master update
           ·   When a warp master value is updated, the warp master calls all its warped object
               and pass them the new master value.

           ·   Then each warped object modifies properties according to the new warp master


       Dominique Dumont, (ddumont at cpan dot org)


       Config::Model::AnyThing, Config::Model::HashId, Config::Model::ListId,
       Config::Model::WarpedNode, Config::Model::Value


       Dominique Dumont


       This software is Copyright (c) 2005-2018 by Dominique Dumont.

       This is free software, licensed under:

         The GNU Lesser General Public License, Version 2.1, February 1999