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1 | |
2 | package Moose::Meta::TypeCoercion; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | use metaclass; |
7 | |
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8 | use Moose::Meta::Attribute; |
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9 | use Moose::Util::TypeConstraints (); |
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10 | |
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11 | __PACKAGE__->meta->add_attribute('type_coercion_map' => ( |
12 | reader => 'type_coercion_map', |
13 | default => sub { [] } |
14 | )); |
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15 | |
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16 | __PACKAGE__->meta->add_attribute( |
17 | Moose::Meta::Attribute->new('type_constraint' => ( |
18 | reader => 'type_constraint', |
19 | weak_ref => 1 |
20 | )) |
21 | ); |
22 | |
23 | # private accessor |
24 | __PACKAGE__->meta->add_attribute('compiled_type_coercion' => ( |
25 | accessor => '_compiled_type_coercion' |
26 | )); |
27 | |
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28 | sub new { |
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29 | my $class = shift; |
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30 | my $self = Class::MOP::class_of($class)->new_object(@_); |
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31 | $self->compile_type_coercion; |
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32 | return $self; |
33 | } |
34 | |
35 | sub compile_type_coercion { |
36 | my $self = shift; |
37 | my @coercion_map = @{$self->type_coercion_map}; |
38 | my @coercions; |
39 | while (@coercion_map) { |
40 | my ($constraint_name, $action) = splice(@coercion_map, 0, 2); |
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41 | my $type_constraint = ref $constraint_name ? $constraint_name : Moose::Util::TypeConstraints::find_or_parse_type_constraint($constraint_name); |
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42 | |
43 | unless ( defined $type_constraint ) { |
44 | require Moose; |
45 | Moose->throw_error("Could not find the type constraint ($constraint_name) to coerce from"); |
46 | } |
47 | |
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48 | push @coercions => [ |
49 | $type_constraint->_compiled_type_constraint, |
50 | $action |
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51 | ]; |
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52 | } |
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53 | $self->_compiled_type_coercion(sub { |
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54 | my $thing = shift; |
55 | foreach my $coercion (@coercions) { |
56 | my ($constraint, $converter) = @$coercion; |
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57 | if ($constraint->($thing)) { |
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58 | local $_ = $thing; |
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59 | return $converter->($thing); |
60 | } |
61 | } |
62 | return $thing; |
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63 | }); |
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64 | } |
65 | |
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66 | sub has_coercion_for_type { |
67 | my ($self, $type_name) = @_; |
68 | my %coercion_map = @{$self->type_coercion_map}; |
69 | exists $coercion_map{$type_name} ? 1 : 0; |
70 | } |
71 | |
72 | sub add_type_coercions { |
73 | my ($self, @new_coercion_map) = @_; |
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74 | |
75 | my $coercion_map = $self->type_coercion_map; |
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76 | my %has_coercion = @$coercion_map; |
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77 | |
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78 | while (@new_coercion_map) { |
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79 | my ($constraint_name, $action) = splice(@new_coercion_map, 0, 2); |
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80 | |
81 | if ( exists $has_coercion{$constraint_name} ) { |
82 | require Moose; |
83 | Moose->throw_error("A coercion action already exists for '$constraint_name'") |
84 | } |
85 | |
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86 | push @{$coercion_map} => ($constraint_name, $action); |
87 | } |
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88 | |
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89 | # and re-compile ... |
90 | $self->compile_type_coercion; |
91 | } |
92 | |
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93 | sub coerce { $_[0]->_compiled_type_coercion->($_[1]) } |
94 | |
95 | |
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96 | 1; |
97 | |
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98 | # ABSTRACT: The Moose Type Coercion metaclass |
99 | |
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100 | __END__ |
101 | |
102 | =pod |
103 | |
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104 | =head1 DESCRIPTION |
105 | |
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106 | A type coercion object is basically a mapping of one or more type |
107 | constraints and the associated coercions subroutines. |
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108 | |
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109 | It's unlikely that you will need to instantiate an object of this |
110 | class directly, as it's part of the deep internals of Moose. |
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111 | |
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112 | =head1 METHODS |
113 | |
114 | =over 4 |
115 | |
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116 | =item B<< Moose::Meta::TypeCoercion->new(%options) >> |
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117 | |
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118 | Creates a new type coercion object, based on the options provided. |
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119 | |
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120 | =over 8 |
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121 | |
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122 | =item * type_constraint |
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123 | |
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124 | This is the L<Moose::Meta::TypeConstraint> object for the type that is |
125 | being coerced I<to>. |
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126 | |
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127 | =back |
128 | |
129 | =item B<< $coercion->type_coercion_map >> |
130 | |
131 | This returns the map of type constraints to coercions as an array |
132 | reference. The values of the array alternate between type names and |
133 | subroutine references which implement the coercion. |
134 | |
135 | The value is an array reference because coercions are tried in the |
136 | order they are added. |
137 | |
138 | =item B<< $coercion->type_constraint >> |
139 | |
140 | This returns the L<Moose::Meta::TypeConstraint> that was passed to the |
141 | constructor. |
142 | |
143 | =item B<< $coercion->has_coercion_for_type($type_name) >> |
144 | |
145 | Returns true if the coercion can coerce the named type. |
146 | |
147 | =item B<< $coercion->add_type_coercions( $type_name => $sub, ... ) >> |
148 | |
149 | This method takes a list of type names and subroutine references. If |
150 | the coercion already has a mapping for a given type, it throws an |
151 | exception. |
152 | |
153 | Coercions are actually |
154 | |
155 | =item B<< $coercion->coerce($value) >> |
156 | |
157 | This method takes a value and applies the first valid coercion it |
158 | finds. |
159 | |
160 | This means that if the value could belong to more than type in the |
161 | coercion object, the first coercion added is used. |
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162 | |
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163 | =item B<< Moose::Meta::TypeCoercion->meta >> |
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164 | |
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165 | This will return a L<Class::MOP::Class> instance for this class. |
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166 | |
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167 | =back |
168 | |
169 | =head1 BUGS |
170 | |
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171 | See L<Moose/BUGS> for details on reporting bugs. |
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172 | |
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173 | =cut |