On 2012.06.07.20.21, sono...@fannullone.us wrote:
> Would someone be so kind as to explain the following, or at least point
> me to further reading?
>
> $item =
> $main::global->{open}->{catalog}->SurfDB::split_line($main::global->{form}->{'itemid'});
>
> The part I'm having trouble understanding is
> "$main::global->{open}->{catalog}->". What does that do to the
> split_line
> sub that's being called? What does it do differently than just calling
> SurfDB::split_line($main::global->{form}->{'itemid'}) by itself?
Good question. Let's break this into a few lines that are more-or-less
equivalent:
my $catalog = $main::global->{open}->{catalog};
my $itemid = $main::global->{form}->{'itemid'}
my $item = $catalog->SurfDB::split_line($itemid);
So that is just doing what you did mentally, I think, and clarifies the problem.
If that line was instead:
my $item = $catalog->split_line($itemid);
then this would be a straightforward perl object-oriented call. The $catalog
would be a blessed variable (an instance variable), and split_line would be a
sub (method) in the package (class) that $catalog was blessed with.
But instead we have a package name and sub spelled out explicitly,
"SurfDB::split_line". So rather than perl using the package/class that $catalog
belongs to it will use the SurfDB::split_line sub.
Finally to your last question, how is this different than just calling the
package::sub directly? With a method call the instance variable, in this case
$catalog, always gets passed as the first parameter to the method. Usually
people name it $self. The same thing happens here -- so this is equivalent to:
my $item = SurfDB::split_line($catalog, $itemid);
... I think :)
--Brock
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