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('AAA'); ## Not OK, since AAA is not an Int
50 UniqueID([$set_obj])->check(100); ## OK, since 100 isn't in the set.
52 You can assign the result of a parameterized dependent type to a variable or to
53 another type constraint, as like any other type constraint:
56 my $unique = UniqueID[$set_obj];
57 $unique->check(10); ## OK
58 $unique->check(2); ## Not OK, '2' is already in the set.
61 subtype UniqueInSet, as UniqueID[$set_obj];
62 UniqueInSet->check(99); ## OK
63 UniqueInSet->check(3); ## Not OK, '3' is already in the set.
65 However, you can't use a dependent type constraint to check or validate a value
66 until you've parameterized the dependent value:
68 UniqueID->check(1000); ## Throws exception
69 UniqueID->validate(1000); ## Throws exception also
71 This is a hard exception, rather than just returning a failure message (via the
72 validate method) or a false boolean (via the check method) since I consider an
73 unparameterized type constraint to be more than just an invalid condition. You
74 will have to catch these in an eval if you think you might have them.
76 Afterward, you can use these dependent types on your L<Moose> based classes
77 and set the dependency target to the value of another attribute or method:
79 TDB: Following is tentative
81 package MyApp::MyClass;
84 use MooseX::Dependent (or maybe a role, or traits...?)
85 use MooseX::Types::Moose qw();
86 use MyApp::Types qw(UniqueID Set);
88 has people => (is=>'ro', isa=>Set, required=>1);
89 has id => (is=>'ro', dependent_isa=>UniqueID, required=>1);
91 TODO notes, coerce=>1 should coerce both check value and constraining value
93 Please see the test cases for more examples.
97 A dependent type is a type constraint whose validity is dependent on a second
98 value. You defined the dependent type constraint with a primary type constraint
99 (such as 'Int') a 'constraining' value type constraint (such as a 'Set' object)
100 and a coderef (such as a 'where' clause in your type constraint declaration)
101 which will compare the incoming value to be checked with a value that conforms
102 to the constraining type constraint.
104 Once created, you can use dependent types directly, or in your L<Moose> based
105 attributes and methods (if you are using L<MooseX::Declare>). Attribute traits
106 are available to make it easy to assign the dependency to the value of another
107 attribute or another method.
109 =head1 TYPE CONSTRAINTS
111 All type constraints are defined in L<MooseX::Dependent::Types>. Please see
112 that class for more documentation and examples of how to create type constraint
113 libraries using dependent types.
117 =head1 ATTRIBUTE TRAITS
123 L<Moose>, L<Moose::Meta::TypeConstraints>, L<MooseX::Types>
127 John Napiorkowski, C<< <jjnapiork@cpan.org> >>
129 =head1 COPYRIGHT & LICENSE
131 This program is free software; you can redistribute it and/or modify
132 it under the same terms as Perl itself.