How can I loop through a Perl array of arrays of hashes? - arrays

Question

I would like to print an Array of Arrays of Hashes, so I looked at perldsc, and ended up with
for my $j (0 .. $#aoaoh) {
for my $aref (#aoaoh) {
print '"' . join('","', #$aref[$j]), "\"\n";
}
}
but it doesn't work.
Does anyone know how to do this?

Answer 1

It works as far as you've gone. Adding some test data to your program gives us:
#!/usr/bin/perl
use strict;
use warnings;
my #aoaoh = (
[
{ a => 1, b => 2 },
{ c => 3, d => 4 },
],
[
{ a => 101, b => 102 },
{ c => 103, d => 104 },
],
);
for my $j (0 .. $#aoaoh) {
for my $aref (#aoaoh) {
print '"' . join('","', #$aref[$j]), "\"\n";
}
}
And running that gives:
$ ./aoaoh
"HASH(0x9c45818)"
"HASH(0x9c70c48)"
"HASH(0x9c60418)"
"HASH(0x9c70c08)"
So you've successfully navigated the two levels of arrays and you're just left with the hash references to dereference. Something like this perhaps:
#!/usr/bin/perl
use strict;
use warnings;
my #aoaoh = (
[
{ a => 1, b => 2 },
{ c => 3, d => 4 },
],
[
{ a => 101, b => 102 },
{ c => 103, d => 104 },
],
);
for my $j (0 .. $#aoaoh) {
for my $aref (#aoaoh) {
# print '"' . join('","', #$aref[$j]), "\"\n";
for (keys %{$aref->[$j]}) {
print "$_ -> $aref->[$j]{$_}\n";
}
}
}
Which gives:
$ ./aoaoh
a -> 1
b -> 2
a -> 101
b -> 102
c -> 3
d -> 4
c -> 103
d -> 104
Personally, I'd write it like this as I think it's easier to deal with elements than indexes.
#!/usr/bin/perl
use strict;
use warnings;
my #aoaoh = (
[
{ a => 1, b => 2 },
{ c => 3, d => 4 },
],
[
{ a => 101, b => 102 },
{ c => 103, d => 104 },
],
);
for my $aref (#aoaoh) {
for my $href (#$aref) {
for (keys %{$href}) {
print "$_ -> $href->{$_}\n";
}
}
}

Answer 2

foreach my $aoh (#aoaoh) {
foreach my $hashref ( #{$aoh} ) {
foreach my $key ( keys %{$hashref} ) {
print $key . " => " . $hashref->{$key}, "\n";
}
print "#" x 40, "\n";
}
}
UPDATE: Sorry, it must be array (not array ref)

Answer 3

Have a look at perlreftut, it will help you,
and see the answer below.
#!/usr/bin/perl
use strict;
use warnings;
my #aoaoh = (
[
{ a => 1, b => 2 },
{ c => 3, d => 4 },
],
[
{ a => 101, b => 102 },
{ c => 103, d => 104 },
],
);
for my $j (0 .. $#aoaoh) {
for my $aref (#{$aoaoh[$j]}) {
for my $test (keys %{$aref})
{
print"$test => ${$aref}{$test}\n";
}
}
}
output:
a => 1
b => 2
c => 3
d => 4
a => 101
b => 102
c => 103
d => 104

Answer 4

To loop through the whole kit & caboodle:
use 5.012;
use warnings;
my #array = (
[
{ a => 1, b => 2 },
{ c => 3, d => 4 },
],
[
{ a => 101, b => 102 },
{ c => 103, d => 104 },
],
);
for my $root (#array) {
for my $each_array_of_hashes (#$root) {
for my $k (keys %{ $each_array_of_hashes } ) {
say $k, ' => ', $each_array_of_hashes->{$k};
}
}
}
Is this what you're after?