/usr/share/doc/libmoose-perl/examples/LazyClass.pod is in libmoose-perl 2.0401-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 | package # hide the package from PAUSE
LazyClass::Attribute;
use strict;
use warnings;
use Carp 'confess';
our $VERSION = '0.05';
use base 'Class::MOP::Attribute';
sub initialize_instance_slot {
my ($self, $meta_instance, $instance, $params) = @_;
# if the attr has an init_arg, use that, otherwise,
# use the attributes name itself as the init_arg
my $init_arg = $self->init_arg();
if ( exists $params->{$init_arg} ) {
my $val = $params->{$init_arg};
$meta_instance->set_slot_value($instance, $self->name, $val);
}
}
sub accessor_metaclass { 'LazyClass::Method::Accessor' }
package # hide the package from PAUSE
LazyClass::Method::Accessor;
use strict;
use warnings;
use Carp 'confess';
our $VERSION = '0.01';
use base 'Class::MOP::Method::Accessor';
sub _generate_accessor_method {
my $attr = (shift)->associated_attribute;
my $attr_name = $attr->name;
my $meta_instance = $attr->associated_class->get_meta_instance;
sub {
if (scalar(@_) == 2) {
$meta_instance->set_slot_value($_[0], $attr_name, $_[1]);
}
else {
unless ( $meta_instance->is_slot_initialized($_[0], $attr_name) ) {
my $value = $attr->has_default ? $attr->default($_[0]) : undef;
$meta_instance->set_slot_value($_[0], $attr_name, $value);
}
$meta_instance->get_slot_value($_[0], $attr_name);
}
};
}
sub _generate_reader_method {
my $attr = (shift)->associated_attribute;
my $attr_name = $attr->name;
my $meta_instance = $attr->associated_class->get_meta_instance;
sub {
confess "Cannot assign a value to a read-only accessor" if @_ > 1;
unless ( $meta_instance->is_slot_initialized($_[0], $attr_name) ) {
my $value = $attr->has_default ? $attr->default($_[0]) : undef;
$meta_instance->set_slot_value($_[0], $attr_name, $value);
}
$meta_instance->get_slot_value($_[0], $attr_name);
};
}
package # hide the package from PAUSE
LazyClass::Instance;
use strict;
use warnings;
our $VERSION = '0.01';
use base 'Class::MOP::Instance';
sub initialize_all_slots {}
1;
__END__
=pod
=head1 NAME
LazyClass - An example metaclass with lazy initialization
=head1 SYNOPSIS
package BinaryTree;
use metaclass (
':attribute_metaclass' => 'LazyClass::Attribute',
':instance_metaclass' => 'LazyClass::Instance',
);
BinaryTree->meta->add_attribute('node' => (
accessor => 'node',
init_arg => ':node'
));
BinaryTree->meta->add_attribute('left' => (
reader => 'left',
default => sub { BinaryTree->new() }
));
BinaryTree->meta->add_attribute('right' => (
reader => 'right',
default => sub { BinaryTree->new() }
));
sub new {
my $class = shift;
$class->meta->new_object(@_);
}
# ... later in code
my $btree = BinaryTree->new();
# ... $btree is an empty hash, no keys are initialized yet
=head1 DESCRIPTION
This is an example metclass in which all attributes are created
lazily. This means that no entries are made in the instance HASH
until the last possible moment.
The example above of a binary tree is a good use for such a
metaclass because it allows the class to be space efficient
without complicating the programing of it. This would also be
ideal for a class which has a large amount of attributes,
several of which are optional.
=head1 AUTHORS
Stevan Little E<lt>stevan@iinteractive.comE<gt>
Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright 2006-2008 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=cut
|