Moo-Type checking example from Perl Maven: What should be the expected result?

Perl300 has asked for the wisdom of the Perl Monks concerning the following question:

I was going through the perl maven web resource and from the example about type checking:

examples/mootype/Person.pm

package Person;
use Moo;
 
has name => (is => 'rw');
has age  => (
    is  => 'rw',
    isa => sub {
       die "'$_[0]' is not an integer!"
          if $_[0] !~ /^\d+$/;
    },
);
 
1;
[download]

examples/mootype/student_1.pl

use strict;
use warnings;
use 5.010;
 
use Person;
my $student = Person->new( name => 'Foo', age => 22 );
say $student->name;
say $student->age;
$student->age('young');
say $student->age;
[download]

The expected result stated on the site is that

Foo

isa check for "age" failed: 'young' is not an integer! at Person.pm line 8.

But what I get is

isa check for "age" failed: '22' is not an integer! at ~/bin/../lib/Person.pm line 10.

What I am trying to understand is, has something changed and this result (no presence of first two say) is now expected? Or am I somehow doing it different? I am using same code including `use 5.010` but the version of perl I am on is 5.26.1 and I have added following two lines between `use 5.010` and `use Person`

use FindBin qw($Bin);

use lib "$Bin/../lib";

Comment on Moo-Type checking example from Perl Maven: What should be the expected result? Select or Download Code

Replies are listed 'Best First'.
Re: Moo-Type checking example from Perl Maven: What should be the expected result? by 1nickt (Canon) on Sep 29, 2018 at 02:08 UTC
Hi, Moo's a great choice. Also good to learn by doing, e.g. by writing your own simple `isa` type validator. But as ++choroba says you probably made a typo in your code, a "type typo" I guess. But that's a good illustration of one good reason to use libraries for common functionality. In the case of Moo type checking we have a very powerful and easy to use system in Type::Tiny. Your code could be rewritten as `package Person; use Moo; use Types::Standard 'Int'; has name => (is => 'rw'); has age => (is => 'rw', isa => Int ); 1;` [download] The output is more verbose: `perl -I. 1223262.pl Foo 22 Value "young" did not pass type constraint "Int" (in $self->{"age"}) a +t 1223262.pl line 9 "Int" is a subtype of "Num" "Num" is a subtype of "LaxNum" Value "young" did not pass type constraint "LaxNum" (in $self->{"a +ge"}) "LaxNum" is defined as: (defined($_) && !ref($_) && Scalar::Util:: +looks_like_number($_))` [download] If you want to control the message, you can, by declaring the type yourself. (This would also allow you to disallow people who haven't been born yet!) See Type::Library for more info on that. Hope this helps! The way forward always starts with a minimal test.	[reply] [d/l] [select]
Re^2: Moo-Type checking example from Perl Maven: What should be the expected result? by tobyink (Canon) on Sep 29, 2018 at 21:27 UTC
Thanks for the advertisement. :) I'll also point out that `/^\d+$/` isn't a great integer check. `\d` allows more characters than the digits 0 to 9. It also allows a whole bunch of other Unicode digit characters, which 99% of the time, you probably didn't really intend to allow. So use `/^[0-9]+$/` which is barely any more typing. I'll also just give a quick demo of: `package Person; use Moo; use Types::Standard 'Int'; has name => (is => 'rw'); has age => (is => 'rw', isa => Int->where(q{ $_ > 0 })); 1;` [download] ... as a simple way to prohibit negative integers. Or even: `package Person; use Moo; use Types::Common::Numeric 'PositiveInt'; has name => (is => 'rw'); has age => (is => 'rw', isa => PositiveInt); 1;` [download] Or: `package Person; use Moo; use Types::Common::Numeric 'IntRange'; has name => (is => 'rw'); has age => (is => 'rw', isa => IntRange[0,200]); # 200 is a realisti +c age limit 1;` [download] toby döt ink	[reply] [d/l] [select]
Re^3: Moo-Type checking example from Perl Maven: What should be the expected result? by hippo (Bishop) on Sep 29, 2018 at 21:39 UTC
So use `/^[0-9]+$/` which is barely any more typing. Quite right. There's also an even shorter alternative: `/^\d+$/a` which uses the handy `/a` modifier. This has the added benefit of enforcing ASCII restriction on some other classes too, should they be used in the regex.	[reply] [d/l] [select]
Re^4: Moo-Type checking example from Perl Maven: What should be the expected result? by tobyink (Canon) on Sep 29, 2018 at 21:46 UTC
Re: Moo-Type checking example from Perl Maven: What should be the expected result? by choroba (Cardinal) on Sep 28, 2018 at 22:24 UTC
Are you sure you copied the code correctly? I'm getting the expected error. To get the error about 22, I had to change `!~` to `=~`, or change the `if` to `unless`. ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]
Re: Moo-Type checking example from Perl Maven: What should be the expected result? by NetWallah (Canon) on Sep 29, 2018 at 05:09 UTC
'say' puts stuff to STDOUT. 'die' spews to STDERR. Since outputs are to different devices, the order may be intermingled - usually, STDERR output appears first. You could get your expected output by using 'warn' instead of 'say' (and adding "\n"). Memory fault -- brain fried	[reply]
Re: Moo-Type checking example from Perl Maven: What should be the expected result? by Perl300 (Friar) on Oct 01, 2018 at 15:24 UTC
Thank you all for your valuable inputs which as always helped me in my learning efforts. Journey continues :-)	[reply]


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