Question

I’m having trouble trying to sort a arrayref of hashes based on a value in the hash, the data structure looks like this:

my %usera = (name => 'tom',
             weight=> 10);
my %userb = (name => 'harry',
             weight=> 1);
my %userc = (name => 'peter',
             weight=> 5);
my $users = [];
push(@$users,\%usera,\%userb,\%userc);

I want to sort the results by weight decending, so it would come back in the order of “Tom,Peter,Harry”, but I haven’t had a lot of luck. I tried:

for my $user (sort{ $users->[$a]{'Weight'} <=> $users->[$b]{'Weight'} } @$users){
    .....
}

Which I thought might have worked, but no love there.

Any idea?

TIA!

Answer 1

If you are sorting @$users, your pipelined data comes in terms of elements not subscripts. So, indexing into $users->[$x] is completely unnecessary, not to mention wrong. If you had used warnings, you would have seen Use of reference "HASH(0x2c201e0)" as array index at ... Change your sort to:

use warnings;

foreach my $user (sort { $b->{weight} <=> $a->{weight} } @$users ) {
    ...
}

Also, as mentioned elsewhere Perl hashes are case sensitive. $h->{Weight} and $h->{weight} are two different hash slots.