Your IP : 216.73.216.74
| Current Path : /usr/local/share/man/man3/ |
|
|
| Current File : //usr/local/share/man/man3/Moose::Cookbook::Meta::GlobRef_InstanceMetaclass.3pm |
.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35)
.\"
.\" 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
..
.\" Set up some character translations and predefined strings. \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote. \*(C+ will
.\" give a nicer C++. Capital omega is used to do unbreakable dashes and
.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
. ds -- \(*W-
. ds PI pi
. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
. ds L" ""
. ds R" ""
. ds C` ""
. ds C' ""
'br\}
.el\{\
. ds -- \|\(em\|
. ds PI \(*p
. ds L" ``
. ds R" ''
. 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 3"
.TH Moose::Cookbook::Meta::GlobRef_InstanceMetaclass 3 "2021-11-07" "perl v5.26.3" "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 2.2201
.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 \*(L"slots\*(R"). 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 \s-1CPAN:\s0
.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 <stevan@cpan.org>
.IP "\(bu" 4
Dave Rolsky <autarch@urth.org>
.IP "\(bu" 4
Jesse Luehrs <doy@cpan.org>
.IP "\(bu" 4
Shawn M Moore <sartak@cpan.org>
.IP "\(bu" 4
יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
.IP "\(bu" 4
Karen Etheridge <ether@cpan.org>
.IP "\(bu" 4
Florian Ragwitz <rafl@debian.org>
.IP "\(bu" 4
Hans Dieter Pearcey <hdp@cpan.org>
.IP "\(bu" 4
Chris Prather <chris@prather.org>
.IP "\(bu" 4
Matt S Trout <mstrout@cpan.org>
.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.