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1 | package MooseX::Storage::Engine::Trait::OnlyWhenBuilt; |
2 | use Moose::Role; |
3 | |
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4 | # we should |
5 | # only serialize the attribute if it's already built. So, go ahead |
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6 | # and check if the attribute has a predicate. If so, check if it's |
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7 | # set and then go ahead and look it up. |
8 | around 'collapse_attribute' => sub { |
9 | my ($orig, $self, $attr, @args) = @_; |
10 | |
11 | my $pred = $attr->predicate if $attr->has_predicate; |
12 | if ($pred) { |
13 | return () unless $self->object->$pred(); |
14 | } |
15 | |
16 | return $self->$orig($attr, @args); |
17 | }; |
a473d69d |
18 | |
19 | 1; |
20 | |
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21 | __END__ |
22 | |
23 | =pod |
24 | |
25 | =head1 NAME |
26 | |
27 | MooseX::Storage::Engine::Trait::OnlyWhenBuilt - An engine trait to bypass serialization |
28 | |
29 | =head1 SYNOPSIS |
30 | |
31 | { package Point; |
32 | use Moose; |
33 | use MooseX::Storage; |
34 | |
35 | with Storage( traits => [qw|OnlyWhenBuilt|] ); |
36 | |
37 | has 'x' => (is => 'rw', lazy_build => 1 ); |
38 | has 'y' => (is => 'rw', lazy_build => 1 ); |
39 | has 'z' => (is => 'rw', builder => '_build_z' ); |
40 | |
41 | sub _build_x { 3 } |
42 | sub _build_y { expensive_computation() } |
43 | sub _build_z { 3 } |
44 | } |
45 | |
46 | my $p = Point->new( 'x' => 4 ); |
47 | |
48 | # the result of ->pack will contain: |
49 | # { x => 4, z => 3 } |
50 | $p->pack; |
51 | |
52 | =head1 DESCRIPTION |
53 | |
54 | Sometimes you don't want a particular attribute to be part of the |
55 | serialization if it has not been built yet. If you invoke C<Storage()> |
56 | as outlined in the C<Synopsis>, only attributes that have been built |
57 | (ie, where the predicate returns 'true') will be serialized. |
58 | This avoids any potentially expensive computations. |
59 | |
60 | This trait is applied to an instance of L<MooseX::Storage::Engine>, for the |
61 | user-visible version shown in the SYNOPSIS, see L<MooseX::Storage::Traits::OnlyWhenBuilt> |
62 | |
63 | =head1 METHODS |
64 | |
65 | =head2 Introspection |
66 | |
67 | =over 4 |
68 | |
69 | =item B<meta> |
70 | |
71 | =back |
72 | |
73 | =head1 BUGS |
74 | |
75 | All complex software has bugs lurking in it, and this module is no |
76 | exception. If you find a bug please either email me, or add the bug |
77 | to cpan-RT. |
78 | |
79 | =head1 AUTHOR |
80 | |
81 | Stevan Little E<lt>stevan.little@iinteractive.comE<gt> |
82 | |
83 | =head1 COPYRIGHT AND LICENSE |
84 | |
85 | Copyright 2007-2008 by Infinity Interactive, Inc. |
86 | |
87 | L<http://www.iinteractive.com> |
88 | |
89 | This library is free software; you can redistribute it and/or modify |
90 | it under the same terms as Perl itself. |
91 | |
92 | =cut |
93 | |