.\" -*- mode: troff; coding: utf-8 -*-
.\" Automatically generated by Pod::Man v6.0.2 (Pod::Simple 3.48)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
.ie n \{\
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds C`
.    ds C'
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\"
.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.\"
.\" Avoid warning from groff about undefined register 'F'.
.de IX
..
.nr rF 0
.if \n(.g .if rF .nr rF 1
.if (\n(rF:(\n(.g==0)) \{\
.    if \nF \{\
.        de IX
.        tm Index:\\$1\t\\n%\t"\\$2"
..
.        if !\nF==2 \{\
.            nr % 0
.            nr F 2
.        \}
.    \}
.\}
.rr rF
.\"
.\" Required to disable full justification in groff 1.23.0.
.if n .ds AD l
.\" ========================================================================
.\"
.IX Title "Moose::Cookbook::Snack::Types 3"
.TH Moose::Cookbook::Snack::Types 3 2026-10-01 "perl v5.44.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\&  package Point;
\&  use Moose;
\&
\&  has \*(Aqx\*(Aq => ( isa => \*(AqInt\*(Aq, is => \*(Aqro\*(Aq );
\&  has \*(Aqy\*(Aq => ( isa => \*(AqInt\*(Aq, is => \*(Aqrw\*(Aq );
\&
\&  package main;
\&  use Try::Tiny;
\&
\&  my $point = try {
\&      Point\->new( x => \*(Aqfifty\*(Aq, y => \*(Aqforty\*(Aq );
\&  }
\&  catch {
\&      print "Oops: $_";
\&  };
\&
\&  my $point;
\&  my $xval             = \*(Aqforty\-two\*(Aq;
\&  my $xattribute       = Point\->meta\->find_attribute_by_name(\*(Aqx\*(Aq);
\&  my $xtype_constraint = $xattribute\->type_constraint;
\&
\&  if ( $xtype_constraint\->check($xval) ) {
\&      $point = Point\->new( x => $xval, y => 0 );
\&  }
\&  else {
\&      print "Value: $xval is not an " . $xtype_constraint\->name . "\en";
\&  }
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This is the Point example from
Moose::Cookbook::Basics::Point_AttributesAndSubclassing with type checking
added.
.PP
If we try to assign a string value to an attribute that is an \f(CW\*(C`Int\*(C'\fR,
Moose will die with an explicit error message. The error will include
the attribute name, as well as the type constraint name and the value
which failed the constraint check.
.PP
We use Try::Tiny to catch this error message.
.PP
Later, we get the Moose::Meta::TypeConstraint object from a
Moose::Meta::Attribute and use the Moose::Meta::TypeConstraint
to check a value directly.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP Moose::Cookbook::Basics::Point_AttributesAndSubclassing 4
.IX Item "Moose::Cookbook::Basics::Point_AttributesAndSubclassing"
.PD 0
.IP Moose::Util::TypeConstraints 4
.IX Item "Moose::Util::TypeConstraints"
.IP Moose::Meta::Attribute 4
.IX Item "Moose::Meta::Attribute"
.PD