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[gitmo/Class-MOP.git] / examples / C3MethodDispatchOrder.pod
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f3f5bd34 1
2package # hide from PAUSE
3 C3MethodDispatchOrder;
4
5use strict;
6use warnings;
7
8use Carp 'confess';
9use Algorithm::C3;
10
2f6d5412 11our $VERSION = '0.03';
f3f5bd34 12
13use base 'Class::MOP::Class';
14
96ceced8 15my $_find_method = sub {
f3f5bd34 16 my ($class, $method) = @_;
17 foreach my $super ($class->class_precedence_list) {
18 return $super->meta->get_method($method)
19 if $super->meta->has_method($method);
20 }
21};
22
a4258ffd 23C3MethodDispatchOrder->meta->add_around_method_modifier('initialize' => sub {
24 my $cont = shift;
25 my $meta = $cont->(@_);
f3f5bd34 26 $meta->add_method('AUTOLOAD' => sub {
27 my $meta = $_[0]->meta;
28 my $method_name;
29 {
30 no strict 'refs';
31 my $label = ${$meta->name . '::AUTOLOAD'};
32 $method_name = (split /\:\:/ => $label)[-1];
33 }
96ceced8 34 my $method = $_find_method->($meta, $method_name);
f3f5bd34 35 (defined $method) || confess "Method ($method_name) not found";
36 goto &$method;
2f6d5412 37 }) unless $meta->has_method('AUTOLOAD');
f3f5bd34 38 $meta->add_method('can' => sub {
96ceced8 39 $_find_method->($_[0]->meta, $_[1]);
2f6d5412 40 }) unless $meta->has_method('can');
a4258ffd 41 return $meta;
42});
f3f5bd34 43
44sub superclasses {
45 my $self = shift;
46 no strict 'refs';
47 if (@_) {
48 my @supers = @_;
a4258ffd 49 @{$self->get_package_variable('@SUPERS')} = @supers;
f3f5bd34 50 }
a4258ffd 51 @{$self->get_package_variable('@SUPERS')};
f3f5bd34 52}
53
54sub class_precedence_list {
55 my $self = shift;
56 return map {
57 $_->name;
58 } Algorithm::C3::merge($self, sub {
59 my $class = shift;
60 map { $_->meta } $class->superclasses;
61 });
62}
63
641;
65
66__END__
67
68=pod
69
70=head1 NAME
71
72C3MethodDispatchOrder - An example attribute metaclass for changing to C3 method dispatch order
73
74=head1 SYNOPSIS
75
76 # a classic diamond inheritence graph
77 #
78 # <A>
79 # / \
80 # <B> <C>
81 # \ /
82 # <D>
83
84 package A;
85 use metaclass 'C3MethodDispatchOrder';
86
87 sub hello { return "Hello from A" }
88
89 package B;
90 use metaclass 'C3MethodDispatchOrder';
91 B->meta->superclasses('A');
92
93 package C;
94 use metaclass 'C3MethodDispatchOrder';
95 C->meta->superclasses('A');
96
97 sub hello { return "Hello from C" }
98
99 package D;
100 use metaclass 'C3MethodDispatchOrder';
101 D->meta->superclasses('B', 'C');
102
103 print join ", " => D->meta->class_precedence_list; # prints C3 order D, B, C, A
104
105 # later in other code ...
106
107 print D->hello; # print 'Hello from C' instead of the normal 'Hello from A'
108
109=head1 DESCRIPTION
110
1c020571 111This is an example of how you could change the method dispatch order of a
112class using L<Class::MOP>. Using the L<Algorithm::C3> module, this repleces
113the normal depth-first left-to-right perl dispatch order with the C3 method
114dispatch order (see the L<Algorithm::C3> or L<Class::C3> docs for more
115information about this).
116
117This example could be used as a template for other method dispatch orders
118as well, all that is required is to write a the C<class_precedence_list> method
119which will return a linearized list of classes to dispatch along.
120
f3f5bd34 121=head1 AUTHOR
122
123Stevan Little E<lt>stevan@iinteractive.comE<gt>
124
125=head1 COPYRIGHT AND LICENSE
126
127Copyright 2006 by Infinity Interactive, Inc.
128
129L<http://www.iinteractive.com>
130
131This library is free software; you can redistribute it and/or modify
132it under the same terms as Perl itself.
133
134=cut