On Fri, Mar 11, 2005 at 04:42:14PM -0800, Wagner, David --- Senior Programmer
Analyst --- WGO wrote:
> Peter Rabbitson wrote:
> > I've been writing a failry complicated data collector with structures
> > as deep as 7 levels, and everything worked very nice for me, until I
> > started cleaning the subroutine interfaces, so they would pass
> > references back and forth instead of working on global vars. The
> > following is a sample code:
> >
> > use warnings;
> > use strict;
> >
> > my %batches = ();
> >
> > my $current_batch = 'abc';
> >
> >
> > push @{$batches{$current_batch}{transactions}}, { trans_num => 'a',
> > reference => 'b',
> > card_num => 'c'
> > };
> >
> > _NASTY_SUB (\%{$batches{$current_batch}});
> >
> > exit;
> >
> > sub _NASTY_SUB {
> >
> > my ($hashref) = @_;
> >
> > foreach my $transaction
> > (@{$batches{$current_batch}{transactions}}) {
> >
> > print join (' * ', keys %{$transaction});
> > print "\n-------\n";
> > }
> >
> >
> > foreach my $transaction (@{$hashref}{transactions}) {
> >
> > print join (' * ', keys %{$transaction});
> > print "\n-------\n";
> > }
> To derefence this setup should be something like:
> foreach my $transaction (@{$hashref->{transactions}}) {
>
> print join (' * ', keys %{$transaction});
> print "\n-------\n";
> }
> which prints out:
> reference * card_num * trans_num
> -------
>
> No Errors. You are passing the Reference as you should to the
> subroutine. So to derefence you would use -> or you could do :
> @{$$hashref{transactions}}
> which has the $$ indicating derefencing.
>
> Myself, it seems much easier to use -> but that is my prefernce.
>
> Wags ;)
>
> > }
> >
> >
> > The first foreach in the sub, while using a variable from the main
> > scope works like a charm. The second foreach, while working on the
> > reference, gives me a warning on something that google only says will
> > be removed as of perl 5.10. What is the actual meaning of
> > pseudo-hashes? To me both foreach statements look identical...
> >
> >
> > Peter
>
>
>
Makes sense... I see where I missed a dereference. I actually was never able
to grasp dereferencing using ->, it doesn't follow my logic in a sense (or
very possible I haven't seen any good examples of it). Could you rewrite the
following dereferencing using -> (not a joke, it's a real life example, I am
getting a hash slice so to speak to save myself tons of dereferencing down
the road)
my %cards = %{clone (\%{$sources{${$batch_ref}{by_method}}{card_def}} )};
Thanks
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