Losing a reference to a package instantiation

jimbend has asked for the wisdom of the Perl Monks concerning the following question:

Good day -

I am creating two instances of package Cluster defined below. I thought that the output of the following would yield 'One One'....

$test1 = Cluster->new("One");
print $test1->getClusterName()." ";
$test2 = Cluster->new("Two");
print $test1->getClusterName();
[download]

...but I'm getting..'One Two'. Can someone point out the error of my ways and how to correct this? Many thanks!

package Cluster;

sub new
{
  my $class = shift;
  my $self = {};

  $self{_clusterName} = shift; 
  $self{_verbs} = [];
 
  bless $self, $class;
  return $self;
}

sub getClusterName
{
  my( $self ) = @_;
  return $self{_clusterName};
}
1;
[download]

Comment on Losing a reference to a package instantiation Select or Download Code

Replies are listed 'Best First'.
Re: Losing a reference to a package instantiation by ikegami (Patriarch) on Jan 01, 2010 at 23:23 UTC
Use `use strict; use warnings;`!! You're modifying hash `%self` instead of modifying the hash referenced by `$self`.	[reply] [d/l] [select]
Re: Losing a reference to a package instantiation by Corion (Patriarch) on Jan 01, 2010 at 23:25 UTC
If you used the strict pragma, Perl would tell you what you're doing wrong. You're using two different variables. One, lexical, variable, `$self`, and another, global, variable `%Cluster::self`, which you overwrite with the clustername every time you assign. You might want to take a look at tye's References Quick Reference.	[reply] [d/l] [select]
Re: Losing a reference to a package instantiation by biohisham (Priest) on Jan 01, 2010 at 23:46 UTC
Welcome to The Monastery... You are dealing with %self keys where you actually needed to deal with the referenced anonymous hash $self in the constructor and the `getClusterName()` methods instead because that is what you intended by initializing an anonymous hash via "`$self={}`". Using strictures is note-worthy at discovering such mix-ups. `#"Cluster.pm" use strict; use warnings; package Cluster; sub new { my $class = shift; #The first argument passed to the #new method is the name of the class my $self = {}; $self->{_clusterName} = shift; #Read data passed to constructor $self->{_verbs} = []; bless $self, $class; return $self; } sub getClusterName { my( $self ) = @_; return $self->{_clusterName}; } 1;` [download] `use strict; use warnings; use Cluster; my $test1 = Cluster->new("One"); print $test1->getClusterName()." "; my $test2 = Cluster->new("Two"); print $test1->getClusterName()." "; print $test2->getClusterName();` [download] `#OUTPUT: one One Two` [download] Have a happy Perl journey :)... Excellence is an Endeavor of Persistence. Chance Favors a Prepared Mind.	[reply] [d/l] [select]