NAME<\/a> Moose::Cookbook::Meta::GlobRef_InstanceMetaclass \u2212 Creating a glob reference meta\u2212instance class<\/p>\n version 2.2014<\/p>\n package My::Meta::Instance; This recipe shows how to build your own meta-instance. The meta instance is the metaclass that creates object instances and helps manages access to attribute slots.<\/p>\n In this example, we\u2019re creating a meta-instance that is based on a glob reference rather than a hash reference. This example is largely based on the Piotr Roszatycki\u2019s MooseX::GlobRef module.<\/p>\n Our extension is a role which will be applied to Moose::Meta::Instance, which creates hash reference based objects. We need to override all the methods which make assumptions about the object\u2019s data structure.<\/p>\n The first method we override is “create_instance”:<\/p>\n sub create_instance { This returns an glob reference which has been blessed into our meta-instance\u2019s associated class.<\/p>\n We also override “clone_instance” to create a new array reference:<\/p>\n sub clone_instance { After that, we have a series of methods which mediate access to the object\u2019s slots (attributes are stored in “slots”). In the default instance class, these expect the object to be a hash reference, but we need to change this to expect a glob reference instead.<\/p>\n sub get_slot_value { This level of indirection probably makes our instance class slower<\/i> than the default. However, when attribute access is inlined, this lookup will be cached:<\/p>\n sub inline_slot_access { The code snippet that the “inline_slot_access” method returns will get “eval”\u2019d once per attribute.<\/p>\n Finally, we use this meta-instance in our “MyApp::User” class:<\/p>\n Moose::Util::MetaRole::apply_metaroles( We actually don\u2019t recommend the use of Moose::Util::MetaRole directly in your class in most cases. Typically, this would be provided by a Moose::Exporter\u2212based module which handles applying the role for you.<\/p>\n This recipe shows how to create your own meta-instance class. It\u2019s unlikely that you\u2019ll need to do this yourself, but it\u2019s interesting to take a peek at how Moose works under the hood.<\/p>\n There are a few meta-instance class extensions on CPAN:<\/small><\/p>\n \u2022<\/p>\n<\/td>\n MooseX::Singleton<\/p>\n<\/td>\n This module extends the instance class in order to ensure that the object is a singleton. The instance it uses is still a blessed hash reference.<\/p>\n \u2022<\/p>\n<\/td>\n MooseX::GlobRef<\/p>\n<\/td>\n This module makes the instance a blessed glob reference. This lets you use a handle as an object instance.<\/p>\n \u2022<\/p>\n<\/td>\n Stevan Little \u2022<\/p>\n<\/td>\n Dave Rolsky \u2022<\/p>\n<\/td>\n Jesse Luehrs \u2022<\/p>\n<\/td>\n Shawn M Moore \u2022<\/p>\n<\/td>\n \u00d7\u00d7\u00d7\u00d7 \u00d7\u00a7\u00d7\u00d7\u2019\u00d7\u00d7 (Yuval Kogman) \u2022<\/p>\n<\/td>\n Karen Etheridge \u2022<\/p>\n<\/td>\n Florian Ragwitz \u2022<\/p>\n<\/td>\n Hans Dieter Pearcey \u2022<\/p>\n<\/td>\n
VERSION<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
CONCLUSION<\/a>
SEE ALSO<\/a>
AUTHORS<\/a>
COPYRIGHT AND LICENSE<\/a> <\/p>\n
\nNAME <\/a> <\/h2>\n
VERSION <\/a> <\/h2>\n
SYNOPSIS <\/a> <\/h2>\n
use Scalar::Util qw( weaken );
use Symbol qw( gensym );
use Moose::Role;
sub create_instance {
my $self = shift;
my $sym = gensym();
bless $sym, $self\u2212>_class_name;
}
sub clone_instance {
my ( $self, $instance ) = @_;
my $new_sym = gensym();
%{*$new_sym} = %{*$instance};
bless $new_sym, $self\u2212>_class_name;
}
sub get_slot_value {
my ( $self, $instance, $slot_name ) = @_;
return *$instance\u2212>{$slot_name};
}
sub set_slot_value {
my ( $self, $instance, $slot_name, $value ) = @_;
*$instance\u2212>{$slot_name} = $value;
}
sub deinitialize_slot {
my ( $self, $instance, $slot_name ) = @_;
delete *$instance\u2212>{$slot_name};
}
sub is_slot_initialized {
my ( $self, $instance, $slot_name ) = @_;
exists *$instance\u2212>{$slot_name};
}
sub weaken_slot_value {
my ( $self, $instance, $slot_name ) = @_;
weaken *$instance\u2212>{$slot_name};
}
sub inline_create_instance {
my ( $self, $class_variable ) = @_;
return ‘do { my $sym = Symbol::gensym(); bless $sym, ‘ . $class_variable . ‘ }’;
}
sub inline_slot_access {
my ( $self, $instance, $slot_name ) = @_;
return ‘*{‘ . $instance . ‘}\u2212>{‘ . $slot_name . ‘}’;
}
package MyApp::User;
use Moose;
Moose::Util::MetaRole::apply_metaroles(
for => __PACKAGE__,
class_metaroles => {
instance => [‘My::Meta::Instance’],
},
);
has ‘name’ => (
is => ‘rw’,
isa => ‘Str’,
);
has ‘email’ => (
is => ‘rw’,
isa => ‘Str’,
);<\/p>\nDESCRIPTION <\/a> <\/h2>\n
my $self = shift;
my $sym = gensym();
bless $sym, $self\u2212>_class_name;
}<\/p>\n
my ( $self, $instance ) = @_;
my $new_sym = gensym();
%{*$new_sym} = %{*$instance};
bless $new_sym, $self\u2212>_class_name;
}<\/p>\n
my ( $self, $instance, $slot_name ) = @_;
*$instance\u2212>{$slot_name};
}<\/p>\n
my ( $self, $instance, $slot_name ) = @_;
return ‘*{‘ . $instance . ‘}\u2212>{‘ . $slot_name . ‘}’;
}<\/p>\n
for => __PACKAGE__,
class_metaroles => {
instance => [‘My::Meta::Instance’],
},
);<\/p>\nCONCLUSION <\/a> <\/h2>\n
SEE ALSO <\/a> <\/h2>\n
\n
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\n <\/td>\n \n <\/td>\n \n <\/td>\n<\/tr>\n<\/table>\n AUTHORS <\/a> <\/h2>\n
\n
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