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1 | package MooseX::Singleton::Role::Meta::Class; |
2 | use Moose::Role; |
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3 | use MooseX::Singleton::Role::Meta::Instance; |
4 | use MooseX::Singleton::Role::Meta::Method::Constructor; |
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5 | |
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6 | |
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7 | sub existing_singleton { |
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8 | my ($class) = @_; |
9 | my $pkg = $class->name; |
10 | |
11 | no strict 'refs'; |
12 | |
13 | # create exactly one instance |
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14 | if ( defined ${"$pkg\::singleton"} ) { |
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15 | return ${"$pkg\::singleton"}; |
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16 | } |
17 | |
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18 | return; |
19 | } |
20 | |
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21 | sub clear_singleton { |
22 | my ($class) = @_; |
23 | my $pkg = $class->name; |
24 | no strict 'refs'; |
25 | undef ${"$pkg\::singleton"}; |
26 | } |
27 | |
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28 | override _construct_instance => sub { |
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29 | my ($class) = @_; |
30 | |
31 | # create exactly one instance |
32 | my $existing = $class->existing_singleton; |
33 | return $existing if $existing; |
34 | |
35 | my $pkg = $class->name; |
36 | no strict 'refs'; |
37 | return ${"$pkg\::singleton"} = super; |
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38 | }; |
39 | |
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40 | if ( $Moose::VERSION >= 1.9900 ) { |
41 | override _inline_params => sub { |
42 | my $self = shift; |
43 | |
44 | return |
45 | 'my $existing = do {', |
46 | 'no strict "refs";', |
47 | 'no warnings "once";', |
48 | '\${"$class\::singleton"};', |
49 | '};', |
50 | 'return ${$existing} if ${$existing};', |
51 | super(); |
52 | }; |
53 | |
54 | override _inline_extra_init => sub { |
55 | my $self = shift; |
56 | |
57 | return '${$existing} = $instance;'; |
58 | }; |
59 | } |
60 | |
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61 | no Moose::Role; |
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62 | |
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63 | 1; |
64 | |
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65 | # ABSTRACT: Metaclass role for MooseX::Singleton |
66 | |
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67 | __END__ |
68 | |
69 | =pod |
70 | |
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71 | =head1 DESCRIPTION |
72 | |
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73 | This metaclass role makes sure that there is only ever one instance of an |
74 | object for a singleton class. The first call to C<construct_instance> is run |
75 | normally (and then cached). Subsequent calls will return the cached version. |
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76 | |
77 | =cut |
78 | |