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Dominique Dumont


Config::Model::WarpedNode - Node that change config class properties


version 2.075


 use Config::Model;
 use Log::Log4perl qw(:easy);

 my $model = Config::Model->new;
 foreach (qw/X Y/) {
        name    => "Class$_",
        element => [ foo => {qw/type leaf value_type string/} ]
    name => "MyClass",

    element => [
        master_switch => {
            type       => 'leaf',
            value_type => 'enum',
            choice     => [qw/cX cY/]

        'a_warped_node' => {
            type   => 'warped_node',
            follow => { ms => '! master_switch' },
            rules  => [
                '$ms eq "cX"' => { config_class_name => 'ClassX' },
                '$ms eq "cY"' => { config_class_name => 'ClassY' },


 my $inst = $model->instance(root_class_name => 'MyClass' );
 my $root = $inst->config_root ;

 print "Visible elements: ",join(' ',$root->get_element_name),"\n" ;
 # Visible elements: master_switch

 $root->load( step => 'master_switch=cX' );
 print "Visible elements: ",join(' ',$root->get_element_name),"\n" ;
 # Visible elements: master_switch a_warped_node

 my $node = $root->grab('a_warped_node') ;
 print "a_warped_node class: ",$node->config_class_name,"\n" ;
 # a_warped_node class: ClassX

 $root->load( step => 'master_switch=cY' );
 print "a_warped_node class: ",$node->config_class_name,"\n" ;
 # a_warped_node class: ClassY


This class provides a way to change dynamically the configuration class (or some other properties) of a node. The changes are done according to the model declaration.

This declaration will specify one (or several) leaf in the configuration tree that will trigger the actual property change of the warped node. This leaf is also referred as warp master.

When the warp master(s) value(s) changes, WarpedNode will create an instance of the new class required by the warp master.

If the morph parameter is set, the values held by the old object are (if possible) copied to the new instance of the object using copy_from method.

Warped node can alter the following properties:



WarpedNode should not be created directly.

Warped node model declaration

Parameter overview

A warped node must be declared with the following parameters:


Always set to warped_node.


Grab string leading to the Config::Model::Value warp master. See "Warp follow argument" in Config::Model::Warper for details.


boolean. If 1, WarpedNode will try to recursively copy the value from the old object to the new object using copy_from method. When a copy is not possible, undef values will be assigned to object elements.


Hash or array ref that specify the property change rules according to the warp master(s) value(s). See "Warp rules argument" in Config::Model::Warper for details on how to specify the warp master values (or combination of values).

Effect declaration

For a warped node, the effects are declared with these parameters:


When requested by the warp master,the WarpedNode will create a new object of the type specified by this parameter:

  XZ => { config_class_name => 'SlaveZ' }

If you pass an array ref, the array will contain the class name and constructor arguments :

  XY  => { config_class_name => ['SlaveY', foo => 'bar' ], },

Specify a Perl class to implement the above config class. This Perl Class must inherit Config::Model::Node.

Forwarded methods

The following methods are forwarded to contained node:

fetch_element config_class_name get_element_name has_element is_element_available element_type load fetch_element_value get_type get_cargo_type describe



Return the name of the node (even if warped out).


Returns true if the node hidden behind this warped node is accessible, i.e. the warp master have values so a node was warped in.


Returns the node object hidden behind the warped node. Croaks if the node is not accessible.

load_data ( hash_ref )

Load configuration data with a hash ref. The hash ref key must match the available elements of the node carried by the warped node.


 $model ->create_config_class 
   element =>
     tree_macro => { type => 'leaf',
                     value_type => 'enum',
                     choice     => [qw/XX XY XZ ZZ/]
     bar =>  {
               type => 'warped_node',
               follow => '! tree_macro', 
               morph => 1,
               rules => [
                         XX => { config_class_name 
                                   => [ 'ClassX', 'foo' ,'bar' ]}
                         XY => { config_class_name => 'ClassY'},
                         XZ => { config_class_name => 'ClassZ'}

In the example above we see that:

  • The 'bar' slot can refer to a ClassX, ClassZ or ClassY object.

  • The warper object is the tree_macro attribute of the root of the object tree.

  • When tree_macro is set to ZZ, bar will not be available. Trying to access bar will raise an exception.

  • When tree_macro is changed from ZZ to XX, bar will refer to a brand new ClassX object constructed with ClassX->new(foo => 'bar')

  • Then, if tree_macro is changed from XX to XY, bar will refer to a brand new ClassY object. But in this case, the object will be initialized with most if not all the attributes of ClassX. This copy will be done whenever tree_macro is changed.


Dominique Dumont, (ddumont at cpan dot org)


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


Dominique Dumont


This software is Copyright (c) 2015 by Dominique Dumont.

This is free software, licensed under:

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