Passing Hashes

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

Replies are listed 'Best First'.
Re: Passing Hashes by pg (Canon) on Oct 23, 2004 at 23:45 UTC
Pass hashref like this: `return \%dat;` [download] On the caller side, receive it like this: `$dat = retrive->gather();` [download] But better "use strict" in your code, and my your variables.	[reply] [d/l] [select]
Re: Passing Hashes by TedPride (Priest) on Oct 24, 2004 at 00:49 UTC
Ok, you misspelled retrieve twice, but that isn't the main problem. To pass a hash, you have to pass its contents: `return (%dat); return ('user' => "ironcom", 'password' => "password"); -- %dat = retrieve->gather();` [download] Or pass as a reference and then either use from the reference or dereference: `return \%dat; -- %dat = %{retrieve->gather()}; print $dat{'user'}; $ref = retrieve->gather(); print $ref->{'user'};` [download] I would personally go with the reference method or passing the data directly. Oh yes, and your module will give errors if you don't end it with a returned true, whatever the heck that means. Add the following to the end of your module: `1;`	[reply] [d/l] [select]
Re^2: Passing Hashes by ironcom (Initiate) on Oct 24, 2004 at 00:58 UTC
Thanks Ted :-) the it seems to work now You've all been a big help. I generally don't code object type code, usually its simple shell scripting or administration scripts, so this is a little different for me. Thanks again	[reply]
Re^3: Passing Hashes by pg (Canon) on Oct 24, 2004 at 01:11 UTC
"I generally don't code object type code" But that's not the point. Same rule applies here, which has nothing to do with OO: `use Data::Dumper; use strict; use warnings; my $dat = do_this(); print Dumper($dat); sub do_this { my %dat = ("a", 1, "b", 2); return \%dat; }` [download]	[reply] [d/l]
Re: Passing Hashes by Anonymous Monk on Oct 24, 2004 at 00:32 UTC
This didnt seem to work. Here is an exact copy of the code in both files file: index.cgi `#!/usr/bin/perl use fetcher; use strict; print "Content-type: text/html\n\n"; my $dat; if($ENV{'CONTENT_LENGTH'} !=0) { $dat = fetcher->gather(); foreach(keys %dat) { print "$_ = $dat{$_}<br>\n"; } } print <<endofhtml; <form action="index.cgi" method="post"> <input type="text" name="b1"><input type="text" name="b2"> <input type="submit"> </form> endofhtml` [download] file: fetcher.pm `package fetcher; sub gather { my %tmp; $tmp{'name'} = "ironcom"; $tmp{'pwd'} = "pwd"; return \%tmp; } 1;` [download] Now, if I do that using strict It tells me that I need to declare %dat. so then I use my %dat alogn with my $dat and it returns nothing. If I do %dat = fetcher->gather(); it prints HASH(0x8230e2c) = Any other suggestions	[reply] [d/l] [select]
Re^2: Passing Hashes by Joost (Canon) on Oct 24, 2004 at 00:47 UTC
You are confused because of the difference between hash references and hashes. `foreach (keys %$dat) { print "$_ = $dat->{$_}<br>\n"; }` [download] As for suggestions: read perldoc perldata, perldoc perlref, perldoc perlsec, use CGI and please `use strict` in all your modules. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l] [select]
Re^2: Passing Hashes by Fletch (Bishop) on Oct 24, 2004 at 00:40 UTC
It doesn't work because the scalar `$dat` you've declared has nothing to do with the hash `%dat`. Hashes and scalars (and arrays for that matter) have completely different namespaces. `$a, @a, %a` all can exist simultaneously and are completely disjoint from one another. You need to (re-)read `perldoc perldata`.	[reply] [d/l] [select]
Re^2: Passing Hashes by TheEnigma (Pilgrim) on Oct 24, 2004 at 00:51 UTC
`$dat` contains a reference to the hash called `%tmp`, because that's what you returned from gather when you (correctly) said `return \%tmp;`. So you need to dereference it when you use it. To dereference `$dat` as a hash, you would say `foreach(keys %$dat)`. TheEnigma	[reply] [d/l] [select]