Hashes in Objects

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

Dear Monks

I have read many things on perl objects and have made a few. But I am perplexed at how to do hashes inside the object.

To give example I want the self hash to have a hash inside it to store things. I would greatly appreciate an example constructor, and get and set methods by key and possibly how to get the hash for internal methods


sub new
{
     my $self  = {};
     
     #error reporting and update vars
     $self->{'error_type'}    = undef;
     $self->{'error_string'}  = undef;

     $self->{'text'}          = undef;
     $self->{'query'}         = undef;
     $self->{'reference'}     = undef;
        
     $self->{'dbh'}           = undef;
     
     $self->{'tokens'}        = %( how do i do this )
      
     bless ($self);

     return $self;

}

sub set_token
{
       my $self = shift;
    
       $self->{'token'}{'$_[0]'} = $_[1];
}

sub get_token
{
       my $self = shift;
    
       return $self->{'token'}{'$_[0]'};
}

sub get_token_keys
{
       my $self = shift;
    
       keys $self->{'token'};

}
[download]

Comment on Hashes in Objects Download Code

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Re: Hashes in Objects by kilinrax (Deacon) on May 07, 2003 at 15:46 UTC
Use an anonymous hash constructor to create the reference: `$self->{'tokens'} = {};` [download] Have a read through perlref, it should give you a good idea of how to create more complex structures with references.	[reply] [d/l]
Re: Hashes in Objects by halley (Prior) on May 07, 2003 at 15:58 UTC
The above replies gave the answer. Here's a little more context: `sub new { my $proto = shift; my $class = ref($proto) \|\| $proto; my $self = { }; $self->{token} = { a => 5 }; # equivalent to $self->{token} = \%( a => 5 ); return bless($self, $class); }` [download] Minor changes required to your accessors: `sub set_token { my $self = shift; $self->{token}{$_[0]} = $_[1]; } sub get_token { my $self = shift; return $self->{token}{$_[0]}; } sub get_token_keys { my $self = shift; return keys %{$self->{token}}; }` [download] Take out the single quotes, especially around the things you need to evaluate (such as `$_[0]`). Perl used to require quotes on those keys which are barewords, but does not anymore. -- `[ e d @ h a l l e y . c c ]`	[reply] [d/l] [select]
Re: Hashes in Objects by artist (Parson) on May 07, 2003 at 15:50 UTC
Here is the sample code that can get you going. `package Pen; use strict; use warnings; sub new { my $class = shift; my $self = { }; bless $self,$class; } sub set_token { my $self = shift; $self->{token}{$_[0]} = $_[1]; } sub get_token { my $self = shift; return $self->{token}{$_[0]}; } sub get_token_keys { my $self = shift; keys %{$self->{token}}; } package main; my $p = new Pen; $p->set_token( color => 'red'); $p->set_token( price => '10.0'); print $p->get_token( 'color'),"\n"; print join "\t",$p->get_token_keys(),"\n";` [download] artist	[reply] [d/l]
Re: Hashes in Objects by hardburn (Abbot) on May 07, 2003 at 15:46 UTC
You can do `$self->{'tokens'} = { };`, which makes the `tokens` key into an empty hashref. ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer Note: All code is untested, unless otherwise stated	[reply] [d/l] [select]