I've got a class/package called Backup_Drive. It records details of backup files from a WMI Query. I write the following to instantiate it:

$drive = Coles_Backup_Drive->new( \$disk, SPACE_THRESHOLD );
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Now if I add a file reference to it calling the add_full_backup method directly: $drive->add_full_backup( $database_name, $file ); it records the file details into the Class's %_last_full_backups hash and @_full_backup_files array and when I leave the method's scope it doesn't lose the detail. I can keep adding file details.

If I add file by add_file method then the $file reference is passed to the add_full_backup method internally but once out of the latter method's scope the array and hash become empty.

I've tried sending the file as a reference of a reference. I can't take away the my clause because then use strict cracks it. I've tried $self->add_full_backup( $database_name, $file ); I don't understand why the hash and array lose their detail after add_full_backup method is called indirectly but keep the details for the life of the class if called directly.

Below is the class code:

package Backup_Drive;
use strict;

use constant LAST_MODIFIED => 0;
use constant FILE_SIZE => 1;
use constant TRANSACTION_LOG => 'trn';
use constant FULL_BACKUP => 'bak';

# make database backups private
my %_last_full_backups = ();
my @_full_backup_files = [];
my %_trn_backups =();
my $_space_threshold;

sub new{
    my ( $class, @arg ) = @_;
    my $self = bless $arg[0], $class;
    $_space_threshold = $arg[1];
    return $self;
}

sub add_file{
### THIS IS THE PROBLEM WHEN PASSING DETAIL FROM THIS METHOD TO add_fu
+ll_backup ###

    # add the file to the relevant file type data
    my( $self, $database_name, $file ) = @_;
    
    if( lc( $file->Extension ) eq FULL_BACKUP ){
        add_full_backup( $self, $database_name, $file );
    } else {
        add_trn_log( $self, $database_name, $file );
    }
    print "wait\n";
}

sub add_full_backup{
    my( $self, $database_name, $file ) = @_;
    
    # capture the last backup details
    if( exists $_last_full_backups{ $database_name } ){
        # record the file size only if the database backup is more rec
+ent the the one recorded
        if( $_last_full_backups{ $database_name }->[ LAST_MODIFIED ] <
+ $file->LastModified ){
            # one file I found returned an undefined value for its siz
+e. So I defaulted the size to zero.
            $_last_full_backups{ $database_name } = [ $file->LastModif
+ied, defined $file->FileSize ? $file->FileSize : 0 ];
        }
    } else {
        # add new details
        $_last_full_backups{ $database_name } = [ $file->LastModified,
+ defined $file->FileSize ? $file->FileSize : 0 ];
    }
    
    # add file to file list
    push ( @_full_backup_files, $file );
    print "test\n";
}

sub add_trn_log{
    my( $self, $database_name, $file ) = @_;
    
    if( exists $_trn_backups{ $database_name } ){
        $_trn_backups{ $database_name } = [ \$file ];
    } else {
        push( @{ $_trn_backups{ $database_name } }, \$file );
    }
}

sub get_last_backup_modified{
    # return the last modified date for the passed in database
    my( $self, $database_name ) = @_;
    $_last_full_backups{ $database_name }->[ LAST_MODIFIED ];
}

sub get_last_backup_file_size{
    # return the last modified date for the passed in database
    my( $self, $database_name ) = @_;
    $_last_full_backups{ $database_name }->[ FILE_SIZE ];
}

sub need_drive_space{
    # return whether the drive needs space to keep it above the space 
+warning threshold.
    my $self = shift;
    if( _database_space_required() > $$self->FreeSpace ){
        return 1;
    }
    
    return 0;
}

sub _database_space_required{
    my $self = shift;
    my $total = 0;
    my $key;
    
    for $key ( keys %_last_full_backups ){
        $total += get_last_backup_file_size( $key );
    }
    
    $total += $_space_threshold;    # keep above threshold warning siz
+e
    return $total;
}


#__END__

1;
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