Sorting an Array of Hash by multiple keys Perl

Question

I have an array referance containing hashes (i.e. @AOH)

$arr_ref = [ { 'brand' => 'A',                'supplier' => 'X',                'PO' => '2'               },               { 'brand' => 'B',                 'supplier' => 'Y',                 'PO' => '1'                      },               { 'brand' => 'B',                 'supplier' => 'X',                 'PO' => '2'                          },               { 'brand' => 'A',                 'supplier' => 'X',                 'PO' => '1'               },               { 'brand' => 'B',                 'supplier' => 'X',                 'PO' => '1'                          } ]; 

I want to sort it on the basis of all three keys (i.e. brand, supplier and PO). Order of sorting should be brand first, then supplier and then finally on PO.

array referance after sorting should be:

$arr_ref = [ { 'brand' => 'A',                 'supplier' => 'X',                 'PO' => '1'               },               { 'brand' => 'A',                'supplier' => 'X',                'PO' => '2'               },               { 'brand' => 'B',                 'supplier' => 'X',                 'PO' => '1'                          },               { 'brand' => 'B',                 'supplier' => 'X',                 'PO' => '2'                          },                             { 'brand' => 'B',                 'supplier' => 'Y',                 'PO' => '1'                      }, ]; 

Answer 1

Since <=> and cmp return 0 to indicate equality, and that's false, and because Perl's logical Boolean operators return the deciding value instead of just 0 or 1, sorting by multiple keys is as easy as stringing multiple comparisons together with or or ||:

@$arr_ref = sort { $a->{brand}    cmp $b->{brand}    or                     $a->{supplier} cmp $b->{supplier} or                     $a->{PO}       <=> $b->{PO}                   } @$arr_ref; 

I'm assuming that PO is a numeric field, so you use <=> for it instead of cmp.

Answer 2

The following should sort the array reference and place the array back into the $arr_ref:

$arr_ref = [sort by_brand_supplier_PO @$arr_ref];  sub by_brand_supplier_PO {     $a->{brand} cmp $b->{brand} ||     $a->{supplier} cmp $b->{supplier} ||     $a->{PO} <=> $b->{PO} }