.\" -*- mode: troff; coding: utf-8 -*- .\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>. .ie n \{\ . ds C` "" . ds C' "" 'br\} .el\{\ . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "Moose::Cookbook::Meta::GlobRef_InstanceMetaclass 3pm" .TH Moose::Cookbook::Meta::GlobRef_InstanceMetaclass 3pm 2024-01-21 "perl v5.38.2" "User Contributed Perl Documentation" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH NAME Moose::Cookbook::Meta::GlobRef_InstanceMetaclass \- Creating a glob reference meta\-instance class .SH VERSION .IX Header "VERSION" version 2.2207 .SH SYNOPSIS .IX Header "SYNOPSIS" .Vb 1 \& package My::Meta::Instance; \& \& use Scalar::Util qw( weaken ); \& use Symbol qw( gensym ); \& \& use Moose::Role; \& \& sub create_instance { \& my $self = shift; \& my $sym = gensym(); \& bless $sym, $self\->_class_name; \& } \& \& sub clone_instance { \& my ( $self, $instance ) = @_; \& \& my $new_sym = gensym(); \& %{*$new_sym} = %{*$instance}; \& \& bless $new_sym, $self\->_class_name; \& } \& \& sub get_slot_value { \& my ( $self, $instance, $slot_name ) = @_; \& return *$instance\->{$slot_name}; \& } \& \& sub set_slot_value { \& my ( $self, $instance, $slot_name, $value ) = @_; \& *$instance\->{$slot_name} = $value; \& } \& \& sub deinitialize_slot { \& my ( $self, $instance, $slot_name ) = @_; \& delete *$instance\->{$slot_name}; \& } \& \& sub is_slot_initialized { \& my ( $self, $instance, $slot_name ) = @_; \& exists *$instance\->{$slot_name}; \& } \& \& sub weaken_slot_value { \& my ( $self, $instance, $slot_name ) = @_; \& weaken *$instance\->{$slot_name}; \& } \& \& sub inline_create_instance { \& my ( $self, $class_variable ) = @_; \& return \*(Aqdo { my $sym = Symbol::gensym(); bless $sym, \*(Aq . $class_variable . \*(Aq }\*(Aq; \& } \& \& sub inline_slot_access { \& my ( $self, $instance, $slot_name ) = @_; \& return \*(Aq*{\*(Aq . $instance . \*(Aq}\->{\*(Aq . $slot_name . \*(Aq}\*(Aq; \& } \& \& package MyApp::User; \& \& use Moose; \& Moose::Util::MetaRole::apply_metaroles( \& for => _\|_PACKAGE_\|_, \& class_metaroles => { \& instance => [\*(AqMy::Meta::Instance\*(Aq], \& }, \& ); \& \& has \*(Aqname\*(Aq => ( \& is => \*(Aqrw\*(Aq, \& isa => \*(AqStr\*(Aq, \& ); \& \& has \*(Aqemail\*(Aq => ( \& is => \*(Aqrw\*(Aq, \& isa => \*(AqStr\*(Aq, \& ); .Ve .SH DESCRIPTION .IX Header "DESCRIPTION" 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. .PP In this example, we're 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's MooseX::GlobRef module. .PP 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's data structure. .PP The first method we override is \f(CW\*(C`create_instance\*(C'\fR: .PP .Vb 5 \& sub create_instance { \& my $self = shift; \& my $sym = gensym(); \& bless $sym, $self\->_class_name; \& } .Ve .PP This returns an glob reference which has been blessed into our meta-instance's associated class. .PP We also override \f(CW\*(C`clone_instance\*(C'\fR to create a new array reference: .PP .Vb 2 \& sub clone_instance { \& my ( $self, $instance ) = @_; \& \& my $new_sym = gensym(); \& %{*$new_sym} = %{*$instance}; \& \& bless $new_sym, $self\->_class_name; \& } .Ve .PP After that, we have a series of methods which mediate access to the object's 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. .PP .Vb 4 \& sub get_slot_value { \& my ( $self, $instance, $slot_name ) = @_; \& *$instance\->{$slot_name}; \& } .Ve .PP This level of indirection probably makes our instance class \fIslower\fR than the default. However, when attribute access is inlined, this lookup will be cached: .PP .Vb 4 \& sub inline_slot_access { \& my ( $self, $instance, $slot_name ) = @_; \& return \*(Aq*{\*(Aq . $instance . \*(Aq}\->{\*(Aq . $slot_name . \*(Aq}\*(Aq; \& } .Ve .PP The code snippet that the \f(CW\*(C`inline_slot_access\*(C'\fR method returns will get \f(CW\*(C`eval\*(C'\fR'd once per attribute. .PP Finally, we use this meta-instance in our \f(CW\*(C`MyApp::User\*(C'\fR class: .PP .Vb 6 \& Moose::Util::MetaRole::apply_metaroles( \& for => _\|_PACKAGE_\|_, \& class_metaroles => { \& instance => [\*(AqMy::Meta::Instance\*(Aq], \& }, \& ); .Ve .PP We actually don't recommend the use of Moose::Util::MetaRole directly in your class in most cases. Typically, this would be provided by a Moose::Exporter\-based module which handles applying the role for you. .SH CONCLUSION .IX Header "CONCLUSION" This recipe shows how to create your own meta-instance class. It's unlikely that you'll need to do this yourself, but it's interesting to take a peek at how Moose works under the hood. .SH "SEE ALSO" .IX Header "SEE ALSO" There are a few meta-instance class extensions on CPAN: .IP \(bu 4 MooseX::Singleton .Sp 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. .IP \(bu 4 MooseX::GlobRef .Sp This module makes the instance a blessed glob reference. This lets you use a handle as an object instance. .SH AUTHORS .IX Header "AUTHORS" .IP \(bu 4 Stevan Little .IP \(bu 4 Dave Rolsky .IP \(bu 4 Jesse Luehrs .IP \(bu 4 Shawn M Moore .IP \(bu 4 יובל קוג'מן (Yuval Kogman) .IP \(bu 4 Karen Etheridge .IP \(bu 4 Florian Ragwitz .IP \(bu 4 Hans Dieter Pearcey .IP \(bu 4 Chris Prather .IP \(bu 4 Matt S Trout .SH "COPYRIGHT AND LICENSE" .IX Header "COPYRIGHT AND LICENSE" This software is copyright (c) 2006 by Infinity Interactive, Inc. .PP This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.