References Looping

CodeJunkie has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks
Can anyone tell me how I can loop through this data structure.

I have a structure like this, formed by using XML::Simple to read an XML file. I want to be able to find out how many itemcode values there are in the array.

$config->{bids}->{itemcode}->[0]
$config->{bids}->{itemcode}->[1]
[download]

Can anyone help me out, i'm not too good with references and finding out how to access the values stored in them.

cheers
Tom

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Re: References Looping by VSarkiss (Monsignor) on Apr 06, 2003 at 23:16 UTC
You don't need a loop just to get the number of items. Something like `scalar @{$config->{bids}{itemcode}}`should do the trick. If you just look at the `@{ }` part, you'll notice it's the same way you'd get the number of elements from a "regular" array. Some resources that may help you on your quest to learn more: Perl References Tutorial Perl References Perl Data Structures Cookbook References Quick Reference from good brother tye. Good luck.	[reply] [d/l] [select]
Re: References Looping by perlplexer (Hermit) on Apr 06, 2003 at 23:14 UTC
Loop: `foreach my $item (@{ $config->{bids}{itemcode} }){ print "$item\n"; }` [download] Size: `my $size = @{ $config->{bids}{itemcode} };` [download] --perlplexer	[reply] [d/l] [select]
Re: References Looping by Your Mother (Archbishop) on Apr 07, 2003 at 08:28 UTC
In addition to the great replies above, I'll offer another tidbit. If you aren't sure that your array holds meaningful (defined) information or that it holds unique information (and assuming it needs to), here's something else to try. Not so easy on the eyes, but fun. `my @unique = keys %{ { map {$_ => 1} grep defined, @{ $config->{bids}{itemcode} } } };` [download] Then when you take `scalar @unique` you know that the count represents real values found and only their unique appearance. Drop the `keys` enclosing block and the `map` block if you just want to count plain old defined elements of the "itemcode" array.	[reply] [d/l] [select]
Re: References Looping by JamesNewman (Initiate) on Apr 07, 2003 at 18:21 UTC
Just a couple of extra things to add to the replies; the tutorial section of this site has some good articles about references of particular use might be the "References quick reference" by tye and it maybe easier (to understand at least) if you copy off the array to a proper array, so:- `my @array = @{$config->{bids}{itemcode}};` [download] Doing it this way seems to be a bit slower in perl (why?) but would allow you to use simpler looking code later in the function i.e. `$size = @array; or foreach (@array){ ... }` [download]	[reply] [d/l] [select]
Re: References Looping by signal9 (Pilgrim) on Apr 07, 2003 at 21:32 UTC
I run into a ton of situations like this reporting from databases. You could try handling this like a lookup table: `foreach my $bids( keys %{ $config } ){ foreach my $itemcode( keys %{ $config->{$bids} } ){ foreach my $inner( @{ $config->{$bids}{$itemcode} } ){ print $inner; # If you just want to dump your vals } } }` [download] if you like Adam	[reply] [d/l]