数组哈希中的Perl访问元素

Question

I am trying to access elements of an array of hashes.

This is a dump of my variable $tst

[
  { DESCRIPTION => "Default", ID => 0, NAME => "Default",  VERSION => "1.0" },
  { DESCRIPTION => "",        ID => 1, NAME => "Custom 1", VERSION => "1.1" },
  { DESCRIPTION => "",        ID => 2, NAME => "Custom 2", VERSION => "1.0" },
  { DESCRIPTION => "",        ID => 3, NAME => "Custom 3", VERSION => "6.0" },
  { DESCRIPTION => "",        ID => 4, NAME => "Custom 4", VERSION => "1.0" },
]

I am trying to access the values for the elements. For example if the ID is 4 then return the field NAME .

I tried printing all of the values for ID but it hasn't been working.

I used variations of the Perl code below from looking online

foreach ($tst) {
  print "$_->{'ID'}, \n";
}

And it gives the following error:

Not a HASH reference at file.pl line 22.

Note : line 22 is the print line from above.

Answer 1

You first have to dereference the array of hash. So,

foreach (@$tst) {
    print $_->{ID}, "\n";
}

should print all the IDs.

Answer 2

The answer that you have accepted is correct, but your data structure is such that you can index the array by the ID value. That is to say $tst->[$id]{ID} == $id for all elements.

So, to print the NAME field for the ID 4 you can say

print $tst->[4]{NAME}, "\n";

and you will see

Custom 4

I hope this helps.