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.