Re: reference to an undefined key

[golux]

Hi exilepanda,

You can't do it the way you're trying, because during the creation of the object "$obj" your code is referring to "$obj" itself which doesn't exist yet! That's kind of like trying to define a word by using the same word in its definition:

"A recursive algorithm is an algorithm which recursively calls itself 
+to produce an answer"

You have a couple of choices. The first is to use the second snippet of code you showed (which you already know works, since it waits until the object $obj is fully defined before trying to reference its data).

Or you could construct the object without referencing the object itself:

use strict;
use warnings;

package MakeObject;
use Data::Dumper;

my $rootDir = '/home';
my $userId  = 'smith';
my $appName = 'project';

my $obj = MakeObject->new;

printf "Object contents => %s\n", Dumper($obj);

sub new {
    my $obj = bless {
        Root        =>  $rootDir, 
        UserDir     => "$rootDir/Usr/$userId/",
        UserAppData => "$rootDir/Usr/$userId/$appName/",
    }, shift;

    return $obj;
}

__END__
Output is:

Object contents => $VAR1 = bless( {
                 'Root' => '/home',
                 'UserDir' => '/home/Usr/smith/',
                 'UserAppData' => '/home/Usr/smith/project/'
               }, 'MakeObject' );

Since the latter has the same effect -- it only refers to data which is already defined ($rootDir, $userId and $appName, but not $obj) -- it doesn't create the catch 22 effect of the original code.