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Module Version: 2.125   Source  


Config::Model::Warper - Warp tree properties


version 2.125


 # 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. E.g.:

 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 expression.

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'

Methods ^


This method returns a string describing:

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 value.


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
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