ch13.038_best

来自「Perl Best Practices the source code」· 038_BEST 代码 · 共 38 行

##############################################################################
##   Code fragment (Recommended) from Chapter 13 of "Perl Best Practices"   ##
##     Copyright (c) O'Reilly & Associates, 2005. All Rights Reserved.      ##
##  See: http://www.oreilly.com/pub/a/oreilly/ask_tim/2001/codepolicy.html  ##
##############################################################################


# Standard modules...
use strict;
use warnings;
use IO::Prompt;
use Carp;
use English qw( -no_match_vars );
use Data::Alias;
use Readonly;

Readonly my $MAX_ALLOWED_VALUE => 5;
my $num = 7;

croak( X::TooBig->new( {value=>$num, range=>[0,$MAX_ALLOWED_VALUE]} ) )
    if $num > $MAX_ALLOWED_VALUE;


package X::TooBig;

sub new {
    my ($class, $data) = @_;
    bless $data, $class;
}

use overload (
    q{""} => sub {
        my ($self) = @_;
        return "$self->{value} not in ($self->{range}[0]..$self->{range}[-1])";
    },
);