Question

Moose types are great, but sometimes you need to be more specific. You all know these data type rules: that parameter may only be 'A', 'B' or 'C', or only a currency symbol, or must conform to some regular expression.

Take a look at the following example which has two constrained attributes, one must be either 'm' or 'f', the other must be a valid ISO date. What’s the best way in Moose to specify these constraints? I’d think of the SQL CHECK clause, but AFAICS there is no check keyword in Moose. So I used trigger, but it sounds wrong. Anyone has a better answer?

package Person;
use Moose;

has gender          => is => 'rw', isa => 'Str', trigger =>
    sub { confess 'either m or f' if $_[1] !~ m/^m|f$/ };
has name            => is => 'rw', isa => 'Str';
has dateOfBirth     => is => 'rw', isa => 'Str', trigger =>
    sub { confess 'not an ISO date' if $_[1] !~ m/^\d\d\d\d-\d\d-\d\d$/ };

no Moose;
__PACKAGE__->meta->make_immutable;

package main;
use Test::More;
use Test::Exception;

dies_ok { Person->new( gender => 42 ) } 'gender must be m or f';
dies_ok { Person->new( dateOfBirth => 42 ) } 'must be an ISO date';

done_testing;

Here’s what I wound up using:

package Blabla::Customer;
use Moose::Util::TypeConstraints;
use Moose;

subtype ISODate => as 'Str' => where { /^\d\d\d\d-\d\d-\d\d$/ };

has id              => is => 'rw', isa => 'Str';
has gender          => is => 'rw', isa => enum ['m', 'f'];
has firstname       => is => 'rw', isa => 'Str';
has dateOfBirth     => is => 'rw', isa => 'ISODate';

no Moose;
__PACKAGE__->meta->make_immutable;

This is Moose version 1.19, in case it matters. I got the following warning for the wrong subtype as => 'Str', where => { ... } syntax I erroneously introduced: Calling subtype() with a simple list of parameters is deprecated. So I had to change it a bit according to the fine manual.

Answer 1

Just define your own subtype, and use that.

package Person;

use Moose::Util::TypeConstraints;

use namespace::clean;
use Moose;

has gender => (
  is => 'rw',
  isa => subtype(
    as 'Str',
    where { /^[mf]$/ }
  ),
);
has name => (
  is => 'rw',
  isa => 'Str'
);
has dateOfBirth => (
  is => 'rw',
  isa => subtype(
    as 'Str',
    where { /^\d\d\d\d-\d\d-\d\d$/ }
  ),
);

no Moose;
__PACKAGE__->meta->make_immutable;
1;

package main;
use Test::More;
use Test::Exception;

dies_ok { Person->new( gender => 42 ) } 'gender must be m or f';
dies_ok { Person->new( dateOfBirth => 42 ) } 'must be an ISO date';

done_testing;

Or you could use the MooseX::Types module.

package Person::TypeConstraints;

use MooseX::Types::Moose qw'Str';
use MooseX::Types -declare => [qw'
  Gender ISODate
'];

subtype Gender, (
  as Str,
  where { /^[mf]$/ },
);

subtype ISODate, (
  as Str,
  where { /^\d\d\d\d-\d\d-\d\d$/ }
);
1;

package Person:

use MooseX::Types::Moose qw'Str';
use Person::TypeConstraints qw'Gender ISODate';

use namespace::clean;
use Moose;

has gender => (
  is => 'rw',
  isa => Gender,
);
has name => (
  is => 'rw',
  isa => Str,
);
has dateOfBirth => (
  is => 'rw',
  isa => ISODate,
);

no Moose;
__PACKAGE__->meta->make_immutable;
1;