I wrote PerlX::Maybe precisely for this purpose!

use v5.14;
use strict;
use warnings;

use PerlX::Maybe;

package Foo {
    use Moose;
    has foo => (is => 'ro', default => 'whatever');
}

my $value = 'hello';
print Foo->new(maybe foo => $value)->dump;

$value = undef;
print Foo->new(maybe foo => $value)->dump;

[download]

As you can see, the maybe keyword is applied at the "consumer side" - i.e. in the code that is using the class.

Within the class itself, you could try MooseX::UndefTolerant though that has a major caveat listed in the documentation!

package Cow { use Moo; has name => (is => 'lazy', default => sub { 'Mooington' }) } say Cow->new->name

In reply to Re: Moose and default values by tobyink
in thread Moose and default values by morgon

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