I work a lot with complex data structures. When I need to access a value at some depth nested keys which not guaranteed to exist, I have to write,

sub somefunc {
  my($self, $context) = @_;
  return 1 # assumed just OK, but no further processing
    unless $self->{config}{key1} &&
           $self->{config}{key1}{context} &&
           $self->{config}{key1}{context}{$context} &&
           $self->{config}{key1}{context}{$context}{form};

  my $form = $self->{config}{key1}{context}{$context}{form};

  # I can work with $form
  ...
}
[download]

in order to avoid autovivification. But I'm getting tired to do that in all over the file, for every Perl file I work on, with distinct CDSes. Once I thought that I might need to restructure my data, but it wasn't possible to do so and it's still not possilbe to restructure now. So I come up with this little tool after doing some searching with Super Search and CPAN without satisfying result.

sub is_hash {
  my($hash, @keys) = @_;
  return unless defined $hash && ref($hash) eq 'HASH';
  return $hash unless @keys;

  my $yes;
  for (@keys) {
    $yes = undef,
      last unless ref $hash eq 'HASH' && %{ $hash };

    $yes = undef,
      last unless exists $hash->{$_} &&
                 defined $hash->{$_};

     $yes = 1;
     $hash = $hash->{$_};
  }

  return $yes ? $hash : $yes;
}
[download]

Now I can write,

return 1
  unless my $form = is_hash($self->{config}, 'key1', 'context', $conte
+xt, 'form');
[download]

It's enough for my needs now. It can be extended further to also allow array references in the middle of the chain,

  $somedata, $key1, $key2, $idx3, $key4 ....;
[download]

Or, to let us specify certain ref type (including non-ref) we want so it terminates if the ref type mismatches,

  my $wanted = 'CODE';
  # if key3 has a value but not a CODE ref, it croaks
  my $code = thefunc($somedata, $wanted, 'key1', 'key2', 'key3');
  $code->(@someargs);
[download]

So, if you were on my shoes, was it worth for you?

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