Mixin::ExtraFields::Driver(3)

NAME
Mixin::ExtraFields::Driver - a backend for extra field storage

VERSION
version 0.140003

SYNOPSIS
This is really not something you'd use on your own, it's just used by Mixin::ExtraFields, but if you insist...

  my $driver = Mixin::ExtraFields::Driver::Phlogiston->from_args(\%arg);

  $driver->set($obj, $obj_id, flammable => "very!");

DESCRIPTION
Mixin::ExtraFields::Driver is a base class for drivers used by Mixin::ExtraFields -- hence the name. A driver is expected to store and retrieve data keyed to an object and a name or key. It can store this in any way it likes, and does not need to guarantee persistence across processes.

PERL VERSION
This library should run on perls released even a long time ago. It should work on any version of perl released in the last five years.

Although it may work on older versions of perl, no guarantee is made that the minimum required version will not be increased. The version may be increased for any reason, and there is no promise that patches will be accepted to lower the minimum required perl.

SUBCLASSING
All drivers must implement the four methods listed below. The base class has implementations of these methods which will die noisily ("confess"-ing) when called.

Almost all methods are passed the same data as their first two arguments: $object, the object for which the driver is to find or alter data, and $id, that object's unique id. While this may be slighly redundant, it keeps the id-finding call in one place.

  from_args
  my $driver = Mixin::ExtraFields::Driver::Subclass->from_args(\%arg);

This method must return a driver object appropriate to the given args. It is not called "new" because it need not return a new object for each call to it. Returning identical objects for identical configurations may be safe for some driver implementations, and it is expressly allowed.

The arguments passed to this method are those given as the "driver" option to the "fields" import group in Mixin::ExtraFields, less the "class" option.

  get_all_detailed_extra
  my %extra = $driver->get_all_detailed_extra($object, $id);

This method must return all available information about all existing extra fields for the given object. It must be returned as a list of name/value pairs. The values must be references to hashes. Each hash must have an entry for the key "value" giving the value for that name.

  set_extra
  $driver->set_extra($object, $id, $name, $value);

This method must set the named extra to the given value.

  delete_extra
  $driver->delete_extra($object, $id, $name);

This method must delete the named extra, causing it to cease to exist.

OPTIMIZING
The methods below can all be implemented in terms of those above. If they are not provided by the subclass, basic implementations exist. These implementations may be less efficient than implementations crafted for the specifics of the storage engine behind the driver, so authors of driver subclasses should consider implementing these methods.

  get_all_extra
  my %extra = $driver->get_all_extra($object, $id);

This method behaves like "get_all_detailed_extra", above, but provides the entry's value, not a detailed hashref, as the value for each entry.

  get_extra

  get_detailed_extra
  my $value = $driver->get_extra($object, $id, $name);

  my $hash = $driver->get_detailed_extra($object, $id, $name);

These methods return a single value requested by name, either as the value itself or a detailed hashref describing it.

  get_all_extra_names
  my @names = $driver->get_all_extra_names($object, $id);

This method returns the names of all existing extras for the given object.

  exists_extra
  if ($driver->exists_extra($object, $id, $name)) { ... }

This method returns true if an entry exists for the given name and false otherwise.

  delete_all_extra
  $driver->delete_all_extra($object, $id);

This method deletes all extras for the object, as per the "delete_extra" method.

AUTHOR
Ricardo Signes <cpan@semiotic.systems>

COPYRIGHT AND LICENSE
This software is copyright (c) 2022 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.