ch13.058_prob_ex13.2

Perl Best Practices the source code

##############################################################################
## Example 13.2 (NOT 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  ##
##############################################################################


#  Example 13-2. Minimal X::EOF exception class


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


# Define the class representing end-of-file exceptions...
package X::EOF;
use English qw( -no_match_vars );
use Carp;
 
# Make X::EOF objects stringify to the same message used previously...
use overload (
    q{""} => sub {
        my ($self) = @_;
        return "Filehandle $self->{handle} at EOF $self->{caller_location}";
    },
    fallback => 1,
);
 
# Create a X::EOF exception...
sub new {
    my ($class, $args_ref) = @_;
 
    # Allocate memory for the object and initialize it...
    my %self = %{$args_ref};
 
    # If no filehandle is passed, indicate that it's unknown...
    if (! exists $self{handle}) {
        $self{handle} = '(unknown)';
    }
 
    # Ask Carp::shortmess()where croak() would report the error occurring...
    if (!exists $self{caller_location}) {
        $self{caller_location} = Carp::shortmess();
    }
 
    # Add it to the class and send it on its way...
    return bless \%self, $class;
}
 
# Give access to the handle that was passed into the constructor...
sub get_handle {
    my ($self) = @_;
    return $self->{handle};
}
 
# Test whether the currently propagating exception is of this type...
sub caught {
    my ($this_class) = @_;
 
    use Scalar::Util qw( blessed );
    return if !blessed $EVAL_ERROR;
    return $EVAL_ERROR->isa($this_class);
}


use Carp;
croak( X::EOF->new({}) );