in reply to Why does testing for the existence of hash keys create the keys ?

From the other day see Re: How do you check if a key exists without creating it ?

no autovivification;

if( exists $foo->{bar}{anything}{you}{want} ){
}

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Or

use Data::Diver 'Dive';

if( my $want = Dive( $foo, qw/ bar anything you want / ) ){
...
}

[download]

Replies are listed 'Best First'.
Re^2: I just want to understand why ...
by Anonymous Monk on Oct 08, 2012 at 08:53 UTC

    And then there's the third way which requires some extra typing, but is fine for two-level or three-level hashes:

    my $r = $hashref; # better to use a short variable name here
if($r->{a} and $r->{a}->{b} and exists $r->{a}->{b}->{c}) 
{
# Do something
}

    [download]
[reply]
[d/l]
Re^2: I just want to understand why ...
by Athanasius (Archbishop) on Oct 08, 2012 at 09:15 UTC
    No autovivification.

    Huh?

    18:58 >perl -w -Mstrict -MData::Dumper -E "my $foo; say Dumper($foo); 
+if (exists $foo->{bar}{anything}{you}{want} ) { say 'hi' } say Dumper
+($foo);"
$VAR1 = undef;

$VAR1 = {
          'bar' => {
                     'anything' => {
                                     'you' => {}
                                   }
                   }
        };


19:00 >

    [download]

    Looks like 3 levels of autovivification to me.

    ???

    Update: See below.

    Athanasius <°(((>< contra mundum

[reply]
[d/l]
      And where is no autovivification; in your code?
      لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]
[d/l]

        Oh, OK, I see it now. In the post by Anonymous Monk, “no autovivification” isn’t formatted as code, so I took it as a comment, didn’t realise it is part of the script! Sorry for the noise. (But, I’ve learned something useful. :-) )

        Athanasius <°(((>< contra mundum

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