Real Basic Perl OOP Question

o2bwise has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,

First off, I am kind of discouraged because I posted this twice before, it showed as posted, and then when I went back to check for replies, my post was not present. Was it deleted?

I don’t understand.

Anyway, I am trying to do Perl OOP. I am following Damien Conway’s book. I wrote some very basic code that I think should work and seems compatible with what Conway does in the beginning of his OOP chapter (3). But, I get this error and I am pretty sure whatever I am doing wrong must be something extremely basic.

I am just wondering what is wrong with the code.

The error is in Line 23, which is in sub new. The error is:

Can’t use string (“Message”) as a HASH while “strict refs” in use at line 23.

The following is Line 23:

return $self->{_name};

And the following is all of the code:

#!/usr/bin/perl -w

package Message;
use strict;

sub new
{
    my ($class) = @_;
#    bless {
    my $objref = {
        _name        => $_[1],
        _subject    => $_[2],
        _message    => $_[3],
#    }, $class;
    };
    bless $objref, $class;
    return $objref;
}

sub name
{
    my ($self) = @_;
    return $self->{_name};
}

package main;

use strict;

my $objType = "Message";
my $name = "John Doe";
my $subject = "money";
my $message = "FRN's should be outlawed.";
my $message_obj = Message->new( $name, $subject, $message );

my $name2 = Message->name( $message_obj );
print "\nMy name is $name2\n";
[download]

I’m really stuck so if someone can give me a hand, that would be great.

o2bwise

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Re: Real Basic Perl OOP Question by Zaxo (Archbishop) on Jun 21, 2005 at 22:18 UTC
I'm not sure why you couldn't find your previous post. Merlyn answered your second question there, and I answered the first. As I showed there, you're misusing arguments in right arrow method calls. After Compline, Zaxo	[reply]
Re: Real Basic Perl OOP Question by BUU (Prior) on Jun 21, 2005 at 22:16 UTC
You mean this: node?	[reply]
Re: Real Basic Perl OOP Question by Joost (Canon) on Jun 21, 2005 at 22:18 UTC
First off, I am kind of discouraged because I posted this twice before, it showed as posted, and then when I went back to check for replies, my post was not present. Was it deleted? if you look at your writeups, you can see where your posts are: I can see one post that seems to match this one: REAL Basic Perl OOP Questions. Don't know about the other one, though. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re: Real Basic Perl OOP Question by Codon (Friar) on Jun 21, 2005 at 22:16 UTC
This is a very basic error. bless() returns a blessed reference; it does not operate on the referent. In otherwords, when you do this: `bless $objref, $class` [download] you are not getting the benefits of the bless(). Try this instead: `my $self = bless $objref, $class; return $self;` [download] Ivan Heffner Sr. Software Engineer, DAS Lead WhitePages.com, Inc.	[reply] [d/l] [select]
Re^2: Real Basic Perl OOP Question by fishbot_v2 (Chaplain) on Jun 21, 2005 at 23:08 UTC
That is not correct - `bless` alters its first argument in-place: `use Data::Dumper; my ( $ref1, $ref2 ) = ( {}, {} ); my $ref3 = bless $ref1, 'Foo'; # capturing results bless $ref2, 'Foo'; # in void context print Dumper $ref3; print Dumper $ref2; __END__ # results identical: $VAR1 = bless( {}, 'Foo' ); $VAR1 = bless( {}, 'Foo' );` [download] `bless` returns the reference as a convenience, however it certainly operates on the reference. (It doesn't alter that which is referenced {the "referent"?}... but he's not doing that, and that isn't what you are demonstrating either.)	[reply] [d/l] [select]
Re^3: Real Basic Perl OOP Question by o2bwise (Scribe) on Jun 21, 2005 at 23:45 UTC
This is awesome. I love this site. Thanks, man.	[reply]
Re^3: Real Basic Perl OOP Question by o2bwise (Scribe) on Jun 21, 2005 at 23:48 UTC
My "this is awesome" comment was meant to be a reply to you...	[reply]
Re^2: Real Basic Perl OOP Question by o2bwise (Scribe) on Jun 21, 2005 at 23:42 UTC
Hi Codon, Thank you. Though I am confused. Based on a recommendation by Zaxo (where I posted this before and didn't realize it was available), I changed: `my $name2 = Message->name( $message_obj );` to `my $name2 = $message_obj->name( );` and it worked! :-) Tony	[reply] [d/l] [select]
Re: Real Basic Perl OOP Question by dynamo (Chaplain) on Jun 21, 2005 at 22:21 UTC
I had written a reply here, but going over it I now realize it was incorrect. There's no delete facility, and I don't want to leave misinformation up, so please ignore this node. Or use it as an opportunity to comment on what I should have done rather than write this.	[reply]
Re^2: Real Basic Perl OOP Question by cees (Curate) on Jun 21, 2005 at 22:37 UTC
People make mistakes all the time. Just a couple days ago I made one here, and was promptly (and politely) corrected. The thing is though, seeing the mistake that was made can still help people, as long as it is marked as a mistake. Someone else may be doing the exact same thing, and not realize that what they are doing is potentially wrong. If you look the node where I made my mistake (Re: Image display firefox problem) you'll see that it is clearly marked as being wrong, but people can still tell what I did wrong. You obviously put some effort into your original post, but now it has no chance of ever helping anyone. In the future, I would consider leaving your answer in place and either correcting the mistake, or clearly marking it as wrong.	[reply]
Re^3: Real Basic Perl OOP Question by dynamo (Chaplain) on Jun 21, 2005 at 23:36 UTC
The thing is, the error I made in the original reply was only made because I thought one of the lines above was not commented out when it was. It was a perceptual error on my part. Anyway, thanks for the advice, and especially the example. I didn't think to just strikeout the text of the original.	[reply]