1MooseX::Types::VariantTUasbelre:C:oDnetcrliabruet(e3d)PMeorolseDXo:c:uTmyepnetsa:t:iVoanriantTable::Declare(3)
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6 MooseX::Types::VariantTable::Declare - Declarative sugar for
7 MooseX::Types::VariantTable based methods.
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10 package Awesome;
11 use Moose;
12
13 variant_method dance => Item => sub {
14 # Item is the least derived type in the hierarchy,
15 # every other type subtypes it
16 # this is in effect a fallback
17 return "fallback";
18 };
19
20 # a more specific type
21 variant_method dance => Ballerina => sub {
22 my ( $self, $ballerina, @args ) = @_;
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24 $ballerina; # a value that passed the TC named "Ballerina"
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26 return "pretty!";
27 };
28
29 # also works with objects
30 variant_method dance => $type_object => sub { ... };
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33 This module provides declarative sugar for defining
34 Moose::Meta::Method::VariantTable methods in your Moose classes and
35 roles.
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37 These methods have some semantics:
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39 Declaration
40 The order of the declarations do not matter in most cases.
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42 It is the type hierarchy that defines the order in which the
43 constraints are checked and items dispatched.
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45 However, in the case that two constraints without an explicit
46 relationship between them (one is a subtype of the other) both accept
47 the same value, the one that was declared earlier will win. There is no
48 way around this issue, so be careful what types you use especially when
49 mixing variants form many different sources.
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51 Adding the same type to a variant table twice is an error.
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53 Inheritence
54 When dispatching all of the subclass's variants will be tried before
55 the superclass.
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57 This allows shadowing of types from the superclass even using broader
58 types.
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60 Roles
61 ... are currently broken.
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63 Don't use variant table methods in a role, unless that's the only
64 definition, because in the future variant table merging will happen at
65 role composition time in a role composition like way, so your code will
66 not continue to work the same.
67
69 Hey! The above document had some coding errors, which are explained
70 below:
71
72 Around line 121:
73 =back without =over
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77perl v5.36.0 2022-0M7o-o2s2eX::Types::VariantTable::Declare(3)