NAME

ODG::Layout - Container role for managing metadata

SYNOPSIS

  package My::Layout;
  use Moose;
    with 'ODG::Layout';

    ...install additional attributes, methods and logic...


  package main;

    my $layout = My::Layout->new( { 
        _metadata_ => [ 
            ODG::Metadata->new( { name => 'field_1'  ] ,
            ODG::Metadata->new( { name => 'field_2'  ] ,
        ]
    } );

  # Access the metadata.
    $layout->_metadata_->[0];
    $layout->get(0);
    $layout->field_1;

  ...

DESCRIPTION

ODG::Layout is an container role that defines a record layout. It containter ODG::Metadata objects in an ArrayRef slot called _metadata_. When the slot is populated or changed, two things occur

• an b<index> attribute is added to each of the ODG::Metadata objects. The index attribute indicates the fields position within the layout.

• named based accessors are installed for each of the ODG::Metadata objects

  ODG::Layout is part of the ODG::Record distribution. Here is an object model

   ODG::Record
     |
     |- slot: _data_
     |
     |- slot: _layout_ (container for ODG::Metadata objects )
     |    |
     |    |- slot: _metadata_
     |
     |- slot: _metadata_  ( Refs ODG::Record::_layout_::_metadata_ ) 

SLOTS

_metadata_

ArrayRef[ODG::Metadata] with metaclass Collection::Array.

Standard array methods ( push, pop, shift, ... ) operating on the derived class operate on this slot. The slot can also be accessed with the _metadata_ accessor.

ATTRIBUTES

_index_name

Private. Str. What the attribute is called that is installed in each of the ODG::Metadata objects in _metadata_ slot.

PUBLIC METHODS

new

Constructor method. Can optionally take a _metadata_ Attribute ArrayRef Installs name based accessors. Additionally, installs an index attribute into each of the ODG::Metadata objects in the _metadata_ slot. This allows for accessing the position of the field by name.

Accessor Methods

The _metadata_ can be accessed by name or by position.

  # Name based.
  $layout->field_1;         # Return the ODG::Metadata object
  $layout->field_1->name;   # field_1
  $layout->field_1->index;  # Position in layout.
  
  # Position based
  $layout->_metadata_->[0];      # Returns the first field.
  $layout->get(0);               # Same using MooseX::AttributeHelpers

get, set, push, pop, shift, unshift, insert

This permits the layout defintiion to be built one field at a time or cloned and modified.

See MooseX::AttributeHelpers

clear, delete, empty

See MooseX::AttributeHelpers

count

See MooseX::AttributeHelpers

grep, map, find

See MooseX::AttributeHelpers

PRIVATE METHODS

_create_index

Installs an b<index> attribute in each of each ODG::Metadata object in the _metadata_ slot. The value of the index is the position in that slot.

_install_named_accessors

Installs named based accessors to ODG::Metadata objects in the _metadata_ slot. One accessor is defined and named for each ODG::Metadata object.

Extending

    package My::Layout;
    use Moose;
        with 'ODG::Layout';

TODO

• Private method return values

  Should we provide a return value (T/F) for succes of the private methods.

• Enforce unique metadata names(?)

• Refactor to make ODG::Layout an extensible class rather than a role.

SEE ALSO

ODG::Metadata, ODG::Record, Moose, MooseX::AttributeHelpers;

THANKS

Steven Little, author of Moose

Members of moose@perl.org

AUTHOR

Christopher Brown, <http://www.opendatagroup,com>

COPYRIGHT AND LICENSE

Copyright (C) 2008 by Open Data

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.0 or, at your option, any later version of Perl 5 you may have available.

cpanm ODG::Record

perl -MCPAN -e shell
install ODG::Record