/usr/lib/perl5/Moose/Cookbook/Roles/Recipe2.pod is in libmoose-perl 2.0401-1.
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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 | package Moose::Cookbook::Roles::Recipe2;
# ABSTRACT: Advanced Role Composition - method exclusion and aliasing
=pod
=head1 NAME
Moose::Cookbook::Roles::Recipe2 - Advanced Role Composition - method exclusion and aliasing
=head1 VERSION
version 2.0401
=head1 SYNOPSIS
package Restartable;
use Moose::Role;
has 'is_paused' => (
is => 'rw',
isa => 'Bool',
default => 0,
);
requires 'save_state', 'load_state';
sub stop { 1 }
sub start { 1 }
package Restartable::ButUnreliable;
use Moose::Role;
with 'Restartable' => {
-alias => {
stop => '_stop',
start => '_start'
},
-excludes => [ 'stop', 'start' ],
};
sub stop {
my $self = shift;
$self->explode() if rand(1) > .5;
$self->_stop();
}
sub start {
my $self = shift;
$self->explode() if rand(1) > .5;
$self->_start();
}
package Restartable::ButBroken;
use Moose::Role;
with 'Restartable' => { -excludes => [ 'stop', 'start' ] };
sub stop {
my $self = shift;
$self->explode();
}
sub start {
my $self = shift;
$self->explode();
}
=head1 DESCRIPTION
In this example, we demonstrate how to exercise fine-grained control
over what methods we consume from a role. We have a C<Restartable>
role which provides an C<is_paused> attribute, and two methods,
C<stop> and C<start>.
Then we have two more roles which implement the same interface, each
putting their own spin on the C<stop> and C<start> methods.
In the C<Restartable::ButUnreliable> role, we want to provide a new
implementation of C<stop> and C<start>, but still have access to the
original implementation. To do this, we alias the methods from
C<Restartable> to private methods, and provide wrappers around the
originals (1).
Note that aliasing simply I<adds> a name, so we also need to exclude the
methods with their original names.
with 'Restartable' => {
-alias => {
stop => '_stop',
start => '_start'
},
-excludes => [ 'stop', 'start' ],
};
In the C<Restartable::ButBroken> role, we want to provide an entirely
new behavior for C<stop> and C<start>. We exclude them entirely when
composing the C<Restartable> role into C<Restartable::ButBroken>.
It's worth noting that the C<-excludes> parameter also accepts a single
string as an argument if you just want to exclude one method.
with 'Restartable' => { -excludes => [ 'stop', 'start' ] };
=head1 CONCLUSION
Exclusion and renaming are a power tool that can be handy, especially
when building roles out of other roles. In this example, all of our
roles implement the C<Restartable> role. Each role provides same API,
but each has a different implementation under the hood.
You can also use the method aliasing and excluding features when
composing a role into a class.
=head1 FOOTNOTES
=over 4
=item (1)
The mention of wrapper should tell you that we could do the same thing
using method modifiers, but for the sake of this example, we don't.
=back
=begin testing
{
my $unreliable = Moose::Meta::Class->create_anon_class(
superclasses => [],
roles => [qw/Restartable::ButUnreliable/],
methods => {
explode => sub { }, # nop.
'save_state' => sub { },
'load_state' => sub { },
},
)->new_object();
ok( $unreliable, 'made anon class with Restartable::ButUnreliable role' );
can_ok( $unreliable, qw/start stop/ );
}
{
my $cnt = 0;
my $broken = Moose::Meta::Class->create_anon_class(
superclasses => [],
roles => [qw/Restartable::ButBroken/],
methods => {
explode => sub { $cnt++ },
'save_state' => sub { },
'load_state' => sub { },
},
)->new_object();
ok( $broken, 'made anon class with Restartable::ButBroken role' );
$broken->start();
is( $cnt, 1, '... start called explode' );
$broken->stop();
is( $cnt, 2, '... stop also called explode' );
}
=end testing
=head1 AUTHOR
Moose is maintained by the Moose Cabal, along with the help of many contributors. See L<Moose/CABAL> and L<Moose/CONTRIBUTORS> for details.
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2011 by Infinity Interactive, Inc..
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut
__END__
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