1 package MooseX::UndefTolerant;
6 use MooseX::UndefTolerant::Attribute;
7 use MooseX::UndefTolerant::Class;
8 use MooseX::UndefTolerant::Constructor;
11 my %metaroles = ( attribute => [ 'MooseX::UndefTolerant::Attribute' ] );
12 if ( $Moose::VERSION < 1.9900 ) {
13 $metaroles{constructor} = [ 'MooseX::UndefTolerant::Constructor' ];
16 $metaroles{class} = [ 'MooseX::UndefTolerant::Class' ];
20 Moose::Exporter->setup_import_methods(
21 class_metaroles => \%metaroles,
26 # ABSTRACT: Make your attribute(s) tolerant to undef initialization
35 use MooseX::UndefTolerant;
40 predicate => 'has_name'
43 # Meanwhile, under the city...
46 my $class = My::Class->new(name => undef);
47 $class->has_name # False!
49 Or, if you only want one attribute to have this behaviour:
54 use MooseX::UndefTolerant::Attribute;
57 traits => [ qw(MooseX::UndefTolerant::Attribute)],
60 predicate => 'has_bar'
65 Loading this module in your L<Moose> class makes initialization of your
66 attributes tolerant of undef. If you specify the value of undef to any of
67 the attributes they will not be initialized, effectively behaving as if you
68 had not provided a value at all.
70 You can also apply the 'UndefTolerant' trait to individual attributes. See
71 L<MooseX::UndefTolerant::Attribute> for details.
73 There will be no change in behaviour to any attribute with a type constraint
74 that accepts undef values (for example C<Maybe> types), as it is presumed that
75 since the type is already "undef tolerant", there is no need to avoid
76 initializing the attribute value with C<undef>.
80 I often found myself in this quandry:
92 my $foo = ... # get the param from something
94 my $class = My:Class->new(foo => $foo, bar => 123);
96 What if foo is undefined? I didn't want to change my attribute to be
97 Maybe[Str] and I still want my predicate (C<has_foo>) to work. The only
101 $class = My:Class->new(foo => $foo, bar => 123);
103 $class = My:Class->new(bar => 123);
106 Or some type of codemulch using ternary conditionals. This module allows you
107 to make your attributes more tolerant of undef so that you can keep the first
108 example: have your cake and eat it too!
112 See L<MooseX::UndefTolerant::Attribute>.
116 This extension does not currently work in immutable classes when applying the
117 trait to some (but not all) attributes in the class. This is because the
118 inlined constructor initialization code currently lives in
119 L<Moose::Meta::Method::Constructor>, not L<Moose::Meta::Attribute>. The good
120 news is that this is expected to be changing shortly.
122 =head1 ACKNOWLEDGEMENTS
124 Many thanks to the crew in #moose who talked me through this module:
126 Hans Dieter Pearcey (confound)
132 Dylan Hardison (dylan)
134 Jay Shirley (jshirley)