1 package MooseX::Dependent;
9 our $AUTHORITY = 'cpan:JJNAPIORK';
13 MooseX::Dependent - Dependent L<MooseX::Types> constraints and L<Moose> attributes
17 Given some L<MooseX::Types> declared as:
21 use MooseX::Types::Moose qw(Object, Int);
22 use MooseX::Dependent::Types qw(Dependent);
23 use Moosex::Types -declare => [qw(Set UniqueID)];
32 as Dependent[Int, Set],
35 return $set->find($int) ? 0:1;
38 Assuming 'Set' is a class that creates and manages sets of values (lists of
39 unique but unordered values) with a method '->find($n)', which returns true when
40 $n is a member of the set and which you instantiate like so:
42 my $set_obj = Set->new(1,2,3,4,5); ## 1..5 are member of Set $set_obj'
44 You can then use this $set_obj as a parameter on the previously declared type
45 constraint 'UniqueID'. This $set_obj become part of the constraint (you can't
46 actually use the constraint without it.)
48 UniqueID[$set_obj]->check(1); ## Not OK, since one isn't unique in $set_obj
49 UniqueID[$set_obj]->check(100); ## OK, since 100 isn't in the set.
51 You can assign the result of a parameterized dependent type to a variable or to
52 another type constraint, as like any other type constraint:
55 my $unique = UniqueID[$set_obj];
56 $unique->check(10); ## OK
57 $unique->check(2); ## Not OK, '2' is already in the set.
60 subtype UniqueInSet, as UniqueID[$set_obj];
61 UniqueInSet->check(99); ## OK
62 UniqueInSet->check(3); ## Not OK, '3' is already in the set.
64 However, you can't use a dependent type constraint to check or validate a value
65 until you've parameterized the dependent value:
67 UniqueID->check(1000); ## Throws exception
68 UniqueID->validate(1000); ## Throws exception also
70 This is a hard exception, rather than just returning a failure message (via the
71 validate method) or a false boolean (via the check method) since I consider an
72 unparameterized type constraint to be more than just an invalid condition. You
73 will have to catch these in an eval if you think you might have them.
75 Afterward, you can use these dependent types on your L<Moose> based classes
76 and set the dependency target to the value of another attribute or method:
78 TDB: Following is tentative
80 package MyApp::MyClass;
83 use MooseX::Dependent (or maybe a role, or traits...?)
84 use MooseX::Types::Moose qw();
85 use MyApp::Types qw(UniqueID Set);
87 has people => (is=>'ro', isa=>Set, required=>1);
88 has id => (is=>'ro', dependent_isa=>UniqueID, required=>1);
90 Please see the test cases for more examples.
94 A dependent type is a type constraint whose validity is dependent on a second
95 value. You defined the dependent type constraint with a primary type constraint
96 (such as 'Int') a 'constraining' value type constraint (such as a 'Set' object)
97 and a coderef (such as a 'where' clause in your type constraint declaration)
98 which will compare the incoming value to be checked with a value that conforms
99 to the constraining type constraint.
101 Once created, you can use dependent types directly, or in your L<Moose> based
102 attributes and methods (if you are using L<MooseX::Declare>). Attribute traits
103 are available to make it easy to assign the dependency to the value of another
104 attribute or another method.
106 =head1 TYPE CONSTRAINTS
108 All type constraints are defined in L<MooseX::Dependent::Types>. Please see
109 that class for more documentation and examples of how to create type constraint
110 libraries using dependent types.
114 =head1 ATTRIBUTE TRAITS
120 L<Moose>, L<Moose::Meta::TypeConstraints>, L<MooseX::Types>
124 John Napiorkowski, C<< <jjnapiork@cpan.org> >>
126 =head1 COPYRIGHT & LICENSE
128 This program is free software; you can redistribute it and/or modify
129 it under the same terms as Perl itself.