Passing hash references

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

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Re: Passing hash references by borisz (Canon) on Jan 31, 2005 at 16:07 UTC
Since `$names` is already a hashref, there is no need to reference the reference again. Please change `my $valid_names = &validateNames(\$names);` [download] to `my $valid_names = &validateNames($names);` [download] in your `sub validateNames` you can access the hashref with the -> operator. `sub validateNames{ my $valid_names=shift; print $valid_names->{SCM555}->{email}; print $valid_names->{SCM556}->{name}; }` [download] Boris	[reply] [d/l] [select]
Re^2: Passing hash references by Tanktalus (Canon) on Jan 31, 2005 at 16:23 UTC
Boris, Just to be consistant with the original poster's code style, whether that's the way you do it or not (it happens to be the way I do things, but it seems I'm in the minority ;->), the arrow operator after a close-brace is not required: `print $valid_names->{SCM555}{email};` [download] Rhodium - note, too, that the quotes inside the braces are optional. I prefer without the quotes (unless required - which they are for certain things), but I do recommend consistancy, even if you disagree with other aspects of my coding style ;-) `print $valid_names->{'SCM555'}{'email'};` [download]	[reply] [d/l] [select]
Re: Passing hash references by olivierp (Hermit) on Jan 31, 2005 at 16:21 UTC
tye's References quick reference would be of help here. You should also go through perlreftut and perlref HTH -- Olivier	[reply]
Re: Passing hash references by edoc (Chaplain) on Jan 31, 2005 at 16:14 UTC
I'll hazard a guess that your confusion stems from a single extra character in your code.. `my $valid_names = &validateNames(\$names);` [download] You don't need the '\' before names. It's already a reference as returned by getNames, so you're actually sending a reference-to-a-reference to your function. Change it to: `my $valid_names = &validateNames($names); # or even my $valid_names = validateNames($names);` [download] and you'll be able to access the values in your validateNames function with: `print $valid_names->{SCM555}{name};` [download] cheers, J	[reply] [d/l] [select]
Re: Passing hash references by fauria (Deacon) on Jan 31, 2005 at 16:24 UTC
In general, i access hashrefs values which i dont know their structure by looking at Data::Dumper output, and then: $hashref->{brackets_1}->{brackets_n}{quotes} Regarding books, i really like Perl Cookbook, chapter 5 covers this topic. Also, ive found Merlyn's article List Manipulation, very useful. It was published in April 2004 Linux Magazine issue. Finaly, you can take a look at Steve's place lesson 7. It is really good.	[reply]
Re^2: Passing hash references by EchoAngel (Pilgrim) on Jan 31, 2005 at 20:30 UTC
my $names = &getNames; my $valid_names = &validateNames(\$names); usually, I noticed that &validateNames(\$names); could be &validateNames($names); just to make things easier. However, you can use it, just more messy looking `sub validateNames{ my $valid_names=shift; print Dumper($valid_names); # I want to access ( print ) the data here my $category = (); foreach $category (sort keys %{${$valid_names}}) { print "INFO - $category . Name : " . ${${$valid_names}}{$category +}{'name'} . "\n"; print "INFO - $category . Email : " . ${${$valid_names}}{$catego +ry}{'email'} . "\n"; } }` [download]	[reply] [d/l]
Re: Passing hash references by bgreenlee (Friar) on Jan 31, 2005 at 16:16 UTC
One issue you have is that you're adding a level of indirection by passing a reference to `$names` to `validateNames`, but it's already a reference (to the `%data` hash). So just call `&validateNames($names)`. As for printing the data, you can do this: `for my $key (keys %$valid_names) { print "key: $key\n"; print " name: $valid_names->{$key}{name}\n"; print " email: $valid_names->{$key}{email}\n"; }` [download] Finally, the places to look for more information on data structures and references are: perldata, perldsc, and perlref. -b	[reply] [d/l] [select]


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