hash of objects

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

Dear wise ones

Im new to objects and not that old at hashes so I thought Id
confusicate myself totally trying to make a hash of objects.
I would like to access an element from my list of objects in the following example
using its object name, so I made a hash of objects.

However Ive obviously made a mess somewhere as I keep getting
the error "Can't call method "print" on unblessed reference...

A helping hand is worth 2 in the bush

#!/apps/perl/5.8.3/bin/perl -w

use strict;

### PACKAGE ###
package Register;
sub new {
    my ($class) = @_;
    my $self = {
       _regName             => undef,
       _regID               => undef,
    };
    bless $self, $class;
    return $self;
}
sub regName {
    my ( $self, $regName ) = @_;
    $self->{_regName} = $regName if defined($regName);
    return $self->{_regName};
}
sub regID {
    my ( $self, $regID ) = @_;
    $self->{_regID} = $regID if defined($regID);
    return $self->{_regID};
}
sub print {
   my ($self) = @_;
   if (defined $self->regName)        { printf ("%s\n",$self->regName)
+      };
   if (defined $self->regID)          { printf ("%s\n",$self->regID)  
+      };
}
###################


my @Regs;
$Regs[0] = new Register();  
$Regs[1] = new Register();  

$Regs[0]->regName("CLKEN");    
$Regs[0]->regID("REG3456");
$Regs[1]->regName("IRQEN");    
$Regs[1]->regID("REG4444");

# I want to access the register based on regName and dont want to 
# search the array each time for my register. So make a hash as follow
+s
my %reg_hash;
foreach my $reg (@Regs) {
   $reg_hash{$reg->regName()} = [] unless exists $reg_hash{$reg->regNa
+me()};
   push @{$reg_hash{$reg->regName()}}, $reg;
}

# now to access a register object from the hash
my $curr_reg;
$curr_reg = new Register();  
$curr_reg = \$reg_hash{IRQEN};
$curr_reg->print;  # ERROR!! Can't call method "regID" on unblessed re
+ference at ./hash_of_objects.pl line 54

$curr_reg = $Regs[0];
$curr_reg->print;  # This line is ok, but seems the same to me ?

1;
[download]

Comment on hash of objects Download Code

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Re: hash of objects by kyle (Abbot) on Mar 22, 2007 at 20:19 UTC
Each value of your `%reg_hash` contains a reference to an array with one element—a Register object (I'm assuming you plan to have arrays of more than one object in the future). Here's where you try to use it: `$curr_reg = new Register(); $curr_reg = \$reg_hash{IRQEN};` [download] This creates a new Register object and then immediately destroys it, replacing it with `\$reg_hash{IRQEN}`. That winds up being a reference to a scalar that contains a reference to the array in `%reg_hash`. What you'd want is this: `$curr_reg = $reg_hash{IRQEN}->[0];` [download] That way, `$curr_reg` is the object you're looking for. If you want to loop through every object in the hash's array, you could do that this way: `foreach my $reg ( @{$reg_hash{IRQEN}} ) { $reg->print; }` [download] Hope this helps. Have a look at perlreftut for a tutorial on references.	[reply] [d/l] [select]
Re^2: hash of objects by Stucked (Initiate) on Mar 23, 2007 at 07:44 UTC
Hi Kyle, Thanks for your solution this is exactly what I was looking for Now I can access any register object in my hash using its name ;o) sweet!	[reply]