KiokuDB::TypeMap::Entry::MOP(3pm)			User Contributed Perl Documentation			 KiokuDB::TypeMap::Entry::MOP(3pm)

NAME

       KiokuDB::TypeMap::Entry::MOP - A KiokuDB::TypeMap entry for objects with a metaclass.

SYNOPSIS

	   KiokuDB::TypeMap->new(
	       entries => {
		   'My::Class' => KiokuDB::TypeMap::Entry::MOP->new(
		       intrinsic => 1,
		   ),
	       },
	   );

DESCRIPTION

       This typemap entry handles collapsing and expanding of Moose based objects.

       It supports anonymous classes with runtime roles, the KiokuDB::Role::ID role.

       Code for immutable classes is cached and performs several orders of magnitude better, so make use of "make_immutable" in
       Moose::Meta::Class.

ATTRIBUTES

       intrinsic
	   If true the object will be collapsed as part of its parent, without an ID.

       check_class_versions
	   If true (the default) then class versions will be checked on load and if there is a mismatch between the stored version number and the
	   current version number, the version upgrade handler tables will be used to convert the out of date entry.

       version_table
       class_version_table
	   Tables of handlers.

	   See also KiokuDB::Role::Upgrade::Data and KiokuDB::Role::Upgrade::Handlers::Table for convenience roles that do not require a central
	   table.

	   The first is a global version table (useful when the typemap entry is only handling one class) and the second is a table of tables
	   keyed by the class name.

	   The tables are keyed by version number (as a string, "undef" and "" are considered the same), and the value can be either a code
	   reference that processes the entry to bring it up to date, a hash reference of overridden fields, or a string denoting a version number
	   that this version is equivalent to.

	   Version numbers have no actual ordinal meaning, they are taken as simple string identifiers.

	   If we had 3 versions, 1.0, 1.1 and 2.0, where 1.1 is a minor update to the class that requires no structural changes from 1.0, our
	   table could be written like this:

	       {
		   '1.0' => '1.1', # upgrading the data from 1.0 to 1.1 is a noop
		   '1.1' => sub {
		       my ( $self, %args ) = @_;

		       # manually convert the entry data
		       return $entry->clone(
			   class_version => '2.0',
			   prev => $entry,
			   data => ...,
		       ),
		   },
	       }

	   When an object that was stored as version 1.0 is retrieved from the database, and the current definition of the class has $VERSION 2.0,
	   table declares 1.0 is the same as 1.1, so we search for the handler for 1.1 and apply it.

	   The resulting class has the version 2.0 which is the same as what we have now, so this object can be thawed.

	   The callback is invoked with the following arguments:

	   entry
	       The entry to upgrade.

	   from_version
	       The key under which the handler was found (not necessarily the same as "$entry->class_version").

	   meta
	       The Class::MOP::Class of the entry's class.

	   linker
	       The KiokuDB::Linker instance that is inflating this object.

	       Can be used to retrieve additional required objects (cycles are not a problem but be aware that the objects might not be usable yet
	       at the time of the callback's invocation).

	   When a hash is provided as a handler it'll be used to create an entry like this:

	       $entry->derive(
		   %$handler,
		   data => {
		       %{ $entry->data },
		       %{ $handler->{data} || {} },
		   },
	       );

	   The field "class_version" is required, and "data" must contain a hash:

	       KiokuDB->connect(
		   class_version_table => {
		       Foo => {
			   "0.02" => {
			       class_version => "0.03", # upgrade 0.02 to 0.03
			       data => {
				   a_new_field => "default_value",
			       },
			   },
		       },
		   },
	       );

       write_upgrades
	   If true, after applying version upgrade handlers, the updated entry will be written back to the database.

	   Defaults to false but might default to true in future versions (unless the database is in readonly mode).

perl v5.12.4							    2011-03-31					 KiokuDB::TypeMap::Entry::MOP(3pm)