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

       Ricardo Signes <cpan@semiotic.systems>

       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.

perl v5.36.0                                       2023-01-07                    Mixin::ExtraFields::Driver(3pm)

       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.

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

       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_extraget_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.

       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.

       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.

       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!");

       version 0.140003