Chapter 2

The Class

A class in Perl is nothing more than a package that happens to have subroutines 

meant to be used as methods. Here's an example of BOA::Logger transformed into 

a class.

package BOA::Logger;

use Carp qw(croak);

use IO::File;

# constructor   returns new BOA::Logger objects

sub new {

   my ($pkg, $filename) = @_;

   # initialize $self as a reference to an empty hash

   my $self = {};

   # open the log file and store IO::File object in $self >{fh}

   my $filehandle = IO::File >new(">>$filename");

   croak("Unable to open $filename : $!") unless $filehandle;

   # print startup line

   $filehandle >print("BOA log started: " . localtime(time) . "\n");

   # store the filehandle in $self

   $self >{fh} = $filehandle;

   # set default log_level of one

   $self >{level} = 1;

   # bless $self as an object in $pkg and return it

   bless($self, $pkg);

   return $self;

}

# level method   changes log level for this log object

sub level {

   my ($self, $level) = @_;

   $self >{level} = $level;

}

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