Ricardo SIGNES 😄


Mixin::Historian - a mixin for recording history about objects


version 0.101350


  package My::Object;
  use Mixin::Historian -history => {
    driver => {
      class => 'YourDriver',

  # Later...
  my $object = My::Object->retrieve(1234);

    type     => 'lava damage',
    severity => 'very badly burned',
    volcano  => 'Eyjafjallajokull',


Mixin::Historian is an application of Mixin::ExtraFields. If you're not familiar with it, you should read about it, both in its documentation and in this article about Mixin::ExtraFields.

Generally, it provides simple mechanism for write-only history. Importing the -history group will get you the add_history method, which generally will accept one hashref with at least a type key. This will be passed along to the driver's add_history method.


I have shoehorned an extra layer of functionality into the Historian driver that I use in my employer's code. When initialized, the Historian mixin is told all legal types, something like this:

  type_map => {
    'lava damage' => {
      severity => { required => 1, store_as => 'extra_1' },
      volcano  => { required => 0, store_as => 'extra_2' },

This way, history entries can be validated before writing. The store_as entries indicate how the arguments to add_history are mapped to database columns. The entire argument is also stored in one field as JSON, and a few other attributes are always required (like by_whom) and some are added just in time (like logged_at).

This feature is not yet present in the CPAN library because I have not yet found a suitable decomposition of concerns to make it a component.


  Ricardo Signes <rjbs@cpan.org>


This software is copyright (c) 2010 by Ricardo Signes.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.