use strict;
use warnings;
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If you do that, you'll see that perl wants you to write the hash accesses as $foo->{'bar'}, not %{$foo}->{'bar'}. You'll also see that you want to have our @ISA = ('Vehicle'); I think those are the only things it throws up.

As for your question, $hash_ref->{$key} is an expression for the value you get when looking up the key in the hash. It doesn't return the key itself, but then again, you don't need that since you've just used the key to look up in the hash, so you'll always have it to hand.

If you want to print keys and values, do you'll need to do it explicitly:

foreach my $key (keys %$hash_ref) {
  print "I have $key $hash_ref->{$key}\n";
}
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Good luck.

aha! thanks a lot champ! worked it out!

This and your previous question are both really about OO design. Think about what should be part of the interface for the base class and provide support for that. For example, if you want to have an object describe itself you could do something like:

use strict;
use warnings;

package Vehicle;

sub new {
     my $class = shift;
     
     # Provide some defaults
     my $self = {wheels => 4, engine => 1800, doors => 4};
     return bless $self, $class;
}

sub describe {
     my $self = shift;
     
     return <<"desc";
My engine is $self->{engine}cc.
I have $self->{wheels} wheels and $self->{doors} doors.
desc
}

package Car;

our @ISA = ('Vehicle');

sub new {
     my $class = shift;
     my $self = new Vehicle ($class);
     
     $self->{colour} = 'blue';
     return bless $self, $class;
}

sub describe {
     my $self = shift;
     my $str = $self->SUPER::describe ();
     
     return $str . <<"desc";
My colour is $self->{colour}.
desc
}

package main;

my $car = new Car;

print $car->describe ();
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Prints:

My engine is 1800cc.
I have 4 wheels and 4 doors.
My colour is blue.
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Although actually that is still pretty nasty. Consider what would happen if you needed a bike: no engine and no doors, or even worse a monocycle with only one wheel ("I have 1 wheels and 0 doors.").

A good starting point for some of this stuff is perlboot, but take a look around the Tutorials area too.

within the hash on the left-hand-side

my %hash = qw(Engine 1800cc Doors 4 Color blue);
for my $key (keys %hash){
  print "$key -> $hash{$key}\n";
}
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so how can i use that with my original post?:


my %hash = qw(Engine 1800cc Doors 4 Color blue);
for my $key (keys %hash){
  print "$key -> $hash{$key}\n";
}
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  for my $key (keys %{$car}){
    print "$key -> $car->{$key}\n";
  }
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Directly accessing the attributes of an object like that would likely be considered poor form.

Have a look through the docs and look out for 'getters' and 'setters'.

• perlboot
• perltoot
• perltooc
• perlbot

Object-Oriented Tutorial specifically discusses getters and setters.

updated: added link to tutorial

Erm, %{$hashref}->{'key'} has some extra line noise in it. You'd really want either $car->{'key'}, or alternately ${ $car }{ 'key' }. You don't use the hash sigil when accessing a single element, just like you don't use @array[$idx] to access a single element from an array.</nit>

thanks for the post mate. however thats not quite what im after. that's cheating what you've suggested.
i want those words you added in to come from the hash, not from adding to the print statement.

ie.
%hash => (Engine, 1800cc, Doors, 4, Color, blue)
print %hash
output is:
Engine 1800cc
Doors 4
Color blue

do you see where im coming from?

I wouldn't call it cheating. You've already hardcoded some text and the hash key. Sagacity's suggestion is perfectly reasonable.

You're probably asking the wrong question. "How do I get key values from a hash?" is more likely what you're after.

foreach my $key (keys %$car) {
    print "$key = $car->{$key}\n";
}
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---
my name's not Keith, and I'm not reasonable.

Apart from that, you could write a generic method that returns a string containing both property name and value, in one string. Not that I see much use in it.