CODEWITHSUNDEEP
perlhashdictionary
Arjun Abhynav
Arjun Abhynav

Reputation: 543

Difference between $map{$string} and $map->{$string} in Perl

I have a map structure in Perl, that I'm getting from some utility. The dump of which looks like this:

$VAR1 = {
  'A0' => 'me_one',
  'A2' => 'me_two',
  'A6' => 'me_six'
}

I want to search if a particular key exists in the map. Say I would like to know if A4 is in the map.

Now if I use if (exists $map{'A4'}), I get an error during build, at $map{.

And if I use if (exists $map->{'A4'}), I get no error, and I get the desired result. However everywhere I search on the internet, to check if a key exists in a map, the syntax in Perl is if (exists $map{key})

Now my inference is that what I get from utility is not a map, though still looks like a map to me from the dump. Any one has an idea what's going on? Thank you.

Edit: Thanks to @raina77ow's answer. Adding this to further his explanation.

my %map;
print $map{key};
my $map_ref = \%map; # The reference was what the utility was returning
print $map_ref->{key};

Upvotes: 2

Views: 542

Answers (1)

raina77ow
raina77ow

Reputation: 106453

The $map{key} line is used when you address a specific element of hash %map. For example:

my %map = (
  a => 'a',
  b => 'b'
);
print $map{a}; # 'a'

The $map->{key} line is used when you address a specific element of hashref $map. -> operator is used specifically to 'deference' a reference.

my $map_ref = {
  a => 'a',
  b => 'b'
};
print $map_ref->{a}; # 'a'

Note that in the first case the regular parenthesis are used, in the second case it's curly brackets (to define so-called anonymous hash).

Upvotes: 4

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