CODEWITHSUNDEEP
perlclassoopobjectoverwrite
ashar76
ashar76

Reputation: 23

New perl object overwrites data of previous object

When I create 2 separate Perl object instances the second one is overwriting the data of the first one. I am new to OO Perl so I think I am missing something basic in how I am handling the $self variable inside the class. Why does the data of $ptr2 object overwrite the data of $ptr1 object? Its probably an easy 1 minute answer from Perl experts but I have been beating my head over this. My actual application is supposed to grab a bunch of data from different sources and run some data analysis, so what I have below is a simplified version to show the problem at hand.

I did check one other question related to the same topic below but it seems to be different from my problem.

Below is what I have in the class: 

package TestClass;

sub new {
  my ($object, $file) = @_;
  my $class = ref($object) || $object;
  my $self = { myfile => $file, };
  bless($self, $class);
  return($self);
}
# grabs key-val pairs from file
sub getFileData {
  my($self) = @_;
  open (FILE, "$self->{myfile}" ) or die "Cannot open\n";
  while (my $curline = <FILE>) {
    my @fields = split(/\s+/,$curline);
    $self{$fields[0]} = $fields[1];
  }
  close FILE;
}
# prints key-val pairs to stdout
sub printFileData {
  my($self) = @_;
  foreach my $key (keys %self) {
    print "$key -> $self{$key}\n";
  }
}
1;

Below is how I am calling the class objects: 

use TestClass;

my $ptr1 = TestClass->new("test1.txt");
my $ptr2 = TestClass->new("test2.txt");

$ptr1->getFileData();
print "This is correct for test1.txt\n";
$ptr1->printFileData();

$ptr2->getFileData();

print "This is wrong for test1.txt, test2.txt overwrote test1.txt\n";
$ptr1->printFileData();
$ptr2->printFileData();

test1.txt and test2.txt have single lines 'VAL1 1' and 'VAL1 2' respectively.

Output of the script looks as follows: 

This is correct for test1.txt
VAL1 -> 1
This is wrong for test1.txt, test2.txt overwrote test1.txt
VAL1 -> 2
VAL1 -> 2

Upvotes: 2

Views: 152

Answers (1)

codnodder
codnodder

Reputation: 1675

In TestClass.pm replace all instances of $self{$key} with $self->{$key} (lines 16 and 24), and %self with %$self (line 23).

Your output will look like this:

This is correct for test1.txt
myfile => test1.txt
VAL1 => 1
This is wrong for test1.txt, test2.txt overwrote test1.txt
myfile => test1.txt
VAL1 => 1
myfile => test2.txt
VAL1 => 2

On a side note, if you use strict; Perl will catch these sorts of errors for you.

Upvotes: 6

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