Config::Model::IdElementReference(3pm)

NAME
Config::Model::IdElementReference - Refer to id element(s) and extract keys

SYNOPSIS
 # used from a value class
 element => [
            node_host => { type => 'leaf',
                           value_type => 'reference' ,
                           refer_to => '! host'
                         },
            if   => { type => 'leaf',
                      value_type => 'reference' ,
                      computed_refer_to
                      => { formula => '  ! host:$h if ',
                           variables => { h => '- node_host' }
                         }
                    },
            ],

  # used from checklist
  element => [
              # simple reference, checklist items are given by the
              # keys of my_hash
              refer_to_list => { type => 'check_list',
                                 refer_to => '- my_hash'
                               },

              # checklist items are given by combining my_hash*
              refer_to_2_list
                            => { type => 'check_list',
                                 refer_to => '- my_hash + - my_hash2   + - my_hash3'
                               },
             ]

DESCRIPTION
This class is user by Config::Model::Value to set up an enumerated value where the possible choice depends on the key of a Config::Model::HashId or the content of a Config::Model::ListId object.

This class is also used by Config::Model::CheckList to define the cheklist items from the keys of another hash (or content of a list).

CONSTRUCTOR
Construction is handled by the calling object.

Config class parameters

refer_to
    "refer_to" is used to specify a hash element that will be used as a reference. "refer_to" points to an array or hash element in the configuration tree using the path syntax (See "grab" in Config::Model::Node for details).

computed_refer_to
    When "computed_refer_to" is used, the path is computed using values from several elements in the configuration tree. "computed_refer_to" is a hash with 2 mandatory elements: "formula" and "variables".

The available choice of this (computed or not) reference value is made from the available keys of the refered_to hash element or the values of the refered_to array element.

The example means the the value must correspond to an existing host:

 value_type => 'reference',
 refer_to => '! host'

This example means the the value must correspond to an existing lan within the host whose Id is specified by hostname:

 value_type => 'reference',
 computed_refer_to => { formula => '! host:$a lan',
                        variables => { a => '- hostname' }
                      }

If you need to combine possibilities from several hash, use the ""+"" token to separate 2 paths:

 value_type => 'reference',
 computed_refer_to => { formula => '! host:$a lan + ! host:foobar lan',
                        variables => { a => '- hostname' }
                      }

You can specify "refer_to" or "computed_refer_to" with a "choice" argument so the possible enum value will be the combination of the specified choice and the refered_to values.

Methods

  reference_info
Returns a human readable string with explains how is retrieved the reference. This method is mostly used to construct an error messages.

AUTHOR
Dominique Dumont, (ddumont at cpan dot org)

SEE ALSO
Config::Model, Config::Model::Value, Config::Model::AnyId, Config::Model::CheckList