9.3. Arrays of HashesAn array of hashes is useful when you have a bunch of records that you'd like to access sequentially, and each record itself contains key/value pairs. Arrays of hashes are used less frequently than the other structures in this chapter. 9.3.1. Composition of an Array of HashesYou can create an array of anonymous hashes as follows: To add another hash to the array, you can simply say:@AoH = ( { husband => "barney", wife => "betty", son => "bamm bamm", }, { husband => "george", wife => "jane", son => "elroy", }, { husband => "homer", wife => "marge", son => "bart", }, ); push @AoH, { husband => "fred", wife => "wilma", daughter => "pebbles" }; 9.3.2. Generation of an Array of HashesHere are some techniques for populating an array of hashes. To read from a file with the following format: you could use either of the following two loops:husband=fred friend=barney If you have a subroutine get_next_pair that returns key/value pairs, you can use it to stuff @AoH with either of these two loops:while ( <> ) { $rec = {}; for $field ( split ) { ($key, $value) = split /=/, $field; $rec->{$key} = $value; } push @AoH, $rec; } while ( <> ) { push @AoH, { split /[\s=]+/ }; } You can append new members to an existing hash like so:while ( @fields = get_next_pair() ) { push @AoH, { @fields }; } while (<>) { push @AoH, { get_next_pair($_) }; } $AoH[0]{pet} = "dino"; $AoH[2]{pet} = "santa's little helper"; 9.3.3. Access and Printing of an Array of HashesYou can set a key/value pair of a particular hash as follows: To capitalize the husband of the second array, apply a substitution:$AoH[0]{husband} = "fred"; You can print all of the data as follows:$AoH[1]{husband} =~ s/(\w)/\u$1/; and with indices:for $href ( @AoH ) { print "{ "; for $role ( keys %$href ) { print "$role=$href->{$role} "; } print "}\n"; } for $i ( 0 .. $#AoH ) { print "$i is { "; for $role ( keys %{ $AoH[$i] } ) { print "$role=$AoH[$i]{$role} "; } print "}\n"; } Copyright © 2001 O'Reilly & Associates. All rights reserved. |
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