kdjantzen has asked for the wisdom of the Perl Monks concerning the following question:

Hello,

in a Moose::Role I defined two subtypes 

subtype 'OptInt' => as 'Int';
subtype 'OptStr' => as 'Str';

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With 
use Types::Standard qw(Maybe Str Int OptInt OptStr);

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I want to specify an attribute of a class 
has 'xxx'  => (is => 'rw', 
                   isa => (Maybe[OptInt])->plus_coercions(OptInt, sub{
+ undef }));

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which, understandably, results in the error message 
Could not find sub 'OptInt' to export in package 'Types::Standard' at

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How should I specify my subtypes in order to make the above work?

Thanks for any help.

K.D.J.

Replies are listed 'Best First'.
Re: Moose subtypes
by 1nickt (Canon) on Oct 06, 2016 at 19:23 UTC

    Hi K.D.J.

    Here's how I do it in Moo. The Type::Tiny libs work seamlessly with Moose, I believe, so this code should Moosify as is. 

    package My::Types;

use strict; use warnings;

use parent 'Type::Library';
use Type::Utils; # gets you sugar, 'declare' etc.
use Types::Standard qw/ Maybe Str Int /;

declare 'OptInt', as Maybe[Int], message {'must be integer or nothing'
+};
declare 'OptStr', as Maybe[Str], message {'must be string or nothing'}
+;

1;

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    package My::Class;

use Moo;
use My::Types qw/ :all /;

has optional_numeric_arg => ( is => 'ro', isa => OptInt );
has optional_string_arg  => ( is => 'ro', isa => OptStr );

1;

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    Note that as an added benefit this also gets you an importable is_TypeName function for each type you declare that can be used anywhere for simple data validation.

    ( I believe I first learned of these techniques in This Advent Calendar article. )

    Hope this helps...

    The way forward always starts with a minimal test.
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      Hello 1nickt,

      thanks for the very helpful information.
      Using it I got my code working as I wanted it.

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