Provided by: libconfig-model-perl_2.152-1_all 
NAME
Config::Model::Warper - Warp tree properties
VERSION
version 2.152
SYNOPSIS
# internal class
DESCRIPTION
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
warp_error
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 ?
Registration
• 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.
AUTHOR
Dominique Dumont, (ddumont at cpan dot org)
SEE ALSO
Config::Model::AnyThing, Config::Model::HashId, Config::Model::ListId,
Config::Model::WarpedNode, Config::Model::Value
AUTHOR
Dominique Dumont
COPYRIGHT AND LICENSE
This software is Copyright (c) 2005-2022 by Dominique Dumont.
This is free software, licensed under:
The GNU Lesser General Public License, Version 2.1, February 1999