Config::Model::WarpedNode(3pm)

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

SYNOPSIS
 $model ->create_config_class
  (
   name => 'Class_with_one_changing_node',
   element =>
   [
    tree_macro => {type => 'leaf',
                   value_type => 'enum',
                   choice     => [qw/XY XZ mXY W/]
                  },

    'a_warped_node'
    => {
        type => 'warped_node',
        follow  => '! tree_macro',
        morph   => 1,
        rules => {
                  XY  => { config_class_name => ['SlaveY'], },
                  mXY => {
                          config_class_name   => 'SlaveY',
                          experience => 'intermediate'
                         },
                  XZ => { config_class_name => 'SlaveZ' }
                 }
       },

    'another_warped_node'
    => {
        type => 'warped_node',
        follow  => { tm => '! tree_macro'},
        morph   => 1,
        rules => [
                  '$tm eq "XY"'  => { config_class_name => ['SlaveY'], },
                  '$tm eq "mXY"' => {
                                    config_class_name   => 'SlaveY',
                                    experience => 'intermediate'
                                  },
                  '$tm eq "XZ"'  => { config_class_name => 'SlaveZ' }
                 ]
       },

DESCRIPTION
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 refered 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:

 config_class_name
 experience
 level

Constructor
WarpedNode should not be created directly.

Warped node model declaration

  Parameter overview
A warped node must be declared with the following parameters:

type
    Always set to "warped_node".

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

morph
    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.

rules
    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::WarpedThing 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:

config_class_name
    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' ], },

experience
    Switch the experience of the slot when the object is warped in.

Forwarded methods
The following methods are forwared 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 config_model

Methods

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

  is_accessible
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.

  get_actual_node
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.

EXAMPLE
 $model ->create_config_class
  (
   experience => [ bar => 'advanced'] ,
   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.

AUTHOR
Dominique Dumont, (ddumont at cpan dot org)

SEE ALSO
Config::Model::Instance, Config::Model, Config::Model::HashId, Config::Model::ListId, Config::Model::AnyThing, Config::Model::WarpedThing, Config::Model::WarpedNode, Config::Model::Value