Non-deprecated way to access multi-level hashes

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

Monks,

This works but Perl warns it's deprecated:

push @Names, %names->{$_}{realname}
  foreach (keys %names);
[download]

This provokes a compile error:

push @Names, %names{$_}{realname}
  foreach (keys %names);
[download]

So: what's the proper use ? - Thanks !

Here's the full context:

my @Names;

my %names =
  (
   'Thunder' =>
   {
    realname => "Mario",
   },
   'Storm'   =>
   {
    realname => "Alfredo",
   },

   'Grail'   =>
   {
    realname => "Giuseppe",
   },
  );
[download]

Comment on Non-deprecated way to access multi-level hashes Select or Download Code

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Re: Non-deprecated way to access multi-level hashes by ikegami (Patriarch) on Mar 07, 2006 at 15:10 UTC
`push @Names, $names{$_}{realname} foreach keys %names;` [download] or `push @Names, $_->{realname} foreach values %names;` [download] or `my @Names = map { $_->{realname} } values %names;` [download] The sigil to use is the type being returned. `%hash # The entire hash is a hash. $hash{key} # An element of the hash is a scalar.` [download] See the "Direct" column of this table.	[reply] [d/l] [select]
Re: Non-deprecated way to access multi-level hashes by TimToady (Parson) on Mar 07, 2006 at 15:57 UTC
Oddly enough, this deprecated syntax is much more like how Perl 6 does it, so I wouldn't worry about it too much. It's not like you're thinking about it wrong--it's just that Perl 5 has a weird idea of how sigils interact with references. Still, it'd be nice if your program didn't spit out warning messages...	[reply]
Re: Non-deprecated way to access multi-level hashes by jkva (Chaplain) on Mar 07, 2006 at 15:13 UTC
carcassonne : I'd try `for(keys %names) { push @Names, $names{$_}{realname}; }` [download] Hope this helps.	[reply] [d/l]
Re: Non-deprecated way to access multi-level hashes by markov (Scribe) on Mar 07, 2006 at 15:19 UTC
use map() to slice: my @realnames = map { $_->{realname} } values %names;	[reply]
Re^2: Non-deprecated way to access multi-level hashes by linux454 (Pilgrim) on Mar 07, 2006 at 21:33 UTC
This is the most efficient solution. I wish I could recall exactly where I have read that maps() are more efficient than foreach. Perhaps in Advanced Perl Programming, or not.	[reply]
Re: Non-deprecated way to access multi-level hashes by bobf (Monsignor) on Mar 07, 2006 at 15:21 UTC
If you're trying to get the values of the `realname` key into the @Names array, use map: `my @Names = map { $names{$_}{realname} } keys %names;` [download]	[reply] [d/l] [select]