CODEWITHSUNDEEP
arraysperlhash
Stuart
Stuart

Reputation: 1773

Perl - Set up an array of hashes and access an item in a hash

  1. Are there any syntax errors in the setup of the array of hashes? It didn't give any warnings, but I also cannot print an item, so I hope that the setup isn't the problem.

  2. How can I access eg x inside of list5 to print it?

.

use strict;
use warnings;
my (%list0, %list1, %list2, %list3, %list4, %list5);

%list5 = (
"list" => 5,
"x" => 1,
"y" => 1,
"z" => 0,
);

my @full_list = (%list0, %list1, %list2, %list3, %list4, %list5);

print ??

Upvotes: 0

Views: 84

Answers (2)

Kenosis
Kenosis

Reputation: 6204

The elements of an array of hashes (AoH) are references to those hashes, so you need to populate @full_list with hash references. Given your script, do the following:

my @full_list = \( %list0, %list1, %list2, %list3, %list4, %list5 );

Then, to access "x inside of list5":

print $full_list[5]->{x}; # prints 1

The -> notation is the arrow operator, which dereferences the hash reference in $full_list[5].

To use list5 as the index into @full_list, you can use the constant pragma:

use strict;
use warnings;
use constant list5 => 5;

...

print $full_list[list5]->{x}; # prints 1

Hope this helps!

Upvotes: 3

eemp
eemp

Reputation: 1166

Perhaps, this is helpful:

As you have it defined (@full_list = (%list0, %list1,...);), the dump of the @full_list via

use Data::Dumper;
print Dumper \@full_list;

looks like

$VAR1 = [
      'y',
      1,
      'x',
      1,
      'z',
      0,
      'list',
      5
    ];

where the even elements are your hash keys and the odd element following each is the value. What Kenosis described is probably what you want. But if for some reason, that is just given to you (in another form and you are simplifying it for us here) and you must work with @full_list or an array defined like that, you can get a hash back that consists of keys and values from all the initial hashes.

my %full_list_hash = @full_list;
print $full_list_hash{x};

Upvotes: 0

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