I have had a lot of trouble, and since worked out the problem, however i dont know why my solution works.

The module (below) is supposed to open a logfile with a supplied name (logger->new(name=>'logname')then simply append to the logfile with a couple of strings eg: logger->log('START','Started prgy at $time').

The problem is in the log method. if i write the code: 
        my $fh = $self->{_handle};
        print $fh  "$location, $message. \n";

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it all works and is cool. my question is why cant i use $self->{_handle}directly (rather than $fh) with the print statement? as always any comments on the code are welcome..

most of the style here is copied frim "Object Oriented Perl - Conway".


package Logger;

$VERSION = 1.00;

use strict;
use vars qw( $AUTOLOAD );
use Carp;

{
  #Encapsulated class data

    my %_log_attr =  #      DEFAULT       ACCESSIBILITY
        ( 
          _name         => ['DEFAULT',    'read/write'],
          _handle       => [undef,        'read']
        );

    #is a specirfied object attribute accessible in a given mode
    sub _accessible
    {
      my ($self, $attr, $mode) = @_;
      $_log_attr{$attr}[1] =~ /$mode/
    }

    # Classwide default value for a specified object attributes
    sub _default_for
    {
      my ($self, $attr) = @_;
      $_log_attr{$attr}[2];
    }

    # list of names of all specified object attributes
    sub _standard_keys
    {
        keys %_log_attr;
    }
}
    
sub new {
    my ($caller, %arg) = @_;
    my $caller_is_obj = ref($caller);
    my $class = $caller_is_obj  || $caller;
    my $self  = bless {}, $class;
    foreach my $attrname ($self->_standard_keys() )
    {
      my ($argname) = ($attrname =~ /^_(.*)/);
      if (exists $arg{$argname})     
          { $self->{$attrname} = $arg{$argname} ;
          }
      elsif ($caller_is_obj)
          { $self->{$attrname} = $caller->{$argname}; 
          }
      else
          { $self->{$attrname} = $self->_default_for($attrname) }
    }
    $self->{_handle}=&prepare_file($self);

    return $self;
}

sub prepare_file {

    my $self = shift;
    if ($self->{_name}) {

        my @time=localtime;
        ++$time[4];
        if (length($time[3])eq 1 ) {$time[3]='0'.$time[3]};
        if (length($time[4])eq 1 ) {$time[4]='0'.$time[4]};
        $time[5]=$time[5]+1900;

        my $name = '>>'.$self->{_name}.".".$time[3].$time[4].$time[5].
+'.log';
        local*LOGFILE;
        open(LOGFILE, $name) || undef;
    
        return *LOGFILE; 
    }
    
}

sub log {
    use Data::Dumper;
    #print Dumper(@_);
    
    my ($self, $location, $message) = @_;

    if ($self->{_handle}) {
        my $fh = $self->{_handle};
        print $fh  "$location, $message. \n";

    } else {
        print "Must call logger->new(name=>'<logfile>') before writing
+ log";
    }
}
1

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In reply to dereferencing file handles by Ryszard

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