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Re: Moose: checking parms in object construction

by kevbot (Priest)
on Aug 02, 2017 at 04:28 UTC ( #1196504=note: print w/replies, xml ) Need Help??


in reply to Moose: checking parms in object construction

Hello Marshall,

You can use types to constrain the values of attributes, see Moose::Manual::Types and Moose::Util::TypeConstraints. For example, you could use an anonymous type to ensure that the value of Month is between 1 and 12.

If you need to perform more complex checking of your arguments, then you can define a BUILD method (see Moose::Manual::Construction).
package Appointment; use Moose; # automatically turns on strict and warnings use Moose::Util::TypeConstraints; my @freq_valid = (qw/OneTime Daily Monthly Quarterly/); has 'Month' => ( is => 'ro', isa => subtype( 'Int' => where { $_ > 0 and $_ < 13 +} ), required => 1, ); has 'Day' => ( is => 'ro', isa => 'Int', required => 1, ); has 'Freq' => ( is => 'ro', isa => 'Str', default => 'OneTime', ); sub BUILD { my $self = shift; if ($self->Month == 12 and $self->Day == 1){ die "I'm having a bad Moose day."; } } 1;
UPDATE: Here is an example of using a subtype to check the values of your Freq attribute.
package Appointment; use Moose; # automatically turns on strict and warnings use Moose::Util::TypeConstraints; use List::Util qw/any/; my @freq_valid = (qw/OneTime Daily Monthly Quarterly/); subtype 'AppointmentFreq' => as 'Str' => where { my $arg = $_; any{ $_ eq $arg } @freq_valid } => message { 'The Freq you provided is not valid' }; has 'Month' => ( is => 'ro', isa => subtype( 'Int' => where { $_ > 0 and $_ < 13 +} ), required => 1, ); has 'Day' => ( is => 'ro', isa => 'Int', required => 1, ); has 'Freq' => ( is => 'ro', isa => 'AppointmentFreq', default => 'OneTime', ); sub BUILD { my $self = shift; if ($self->Month == 12 and $self->Day == 1){ die "I'm having a bad Moose day."; } } 1;

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