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.

In reply to Re: Moo-Type checking example from Perl Maven: What should be the expected result? by 1nickt
in thread Moo-Type checking example from Perl Maven: What should be the expected result? by Perl300

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