Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer

Sorting on Nested Element

by dsb (Chaplain)
on Sep 30, 2011 at 16:23 UTC ( #928852=perlquestion: print w/ replies, xml ) Need Help??
dsb has asked for the wisdom of the Perl Monks concerning the following question:

Hello all, I'm trying to sort on a nested key value. Given a data structure that looks like this:
$data = { Elements => { AlphaKey => { Name => 'Foo', Priority => 2, OtherVal => 'randomthings' }, BetaKey => { Name => 'Bar', Priority => 1, OtherVal => 'morerandomthings' }, }};
I want to process them in a sorted order based on the priority value. I'm trying to just turn the hashref into an arrayref, so that it winds up looking like:
$sorted = [ { Name => 'Bar', Priority => 1 OtherVal => 'morerandomthings' }, { Name => 'Foo', Priority => 2, OtherVal => 'randomthings' }, ];
It's easy enough to get a sorted list of priorities:
my @pri = sort { $a <=> $b } map { $data->{Elements}{$_}->{priority} } + keys %{$data->{Elements}};
I'm lost on how to build an arrayref-based structure from there. I'm not even sure i'm going down the right path now that I'm typing it out. Thoughts?

Comment on Sorting on Nested Element
Select or Download Code
Replies are listed 'Best First'.
Re: Sorting on Nested Element
by BrowserUk (Pope) on Sep 30, 2011 at 16:37 UTC
    I'm lost on how to build an arrayref-based structure from there.

    You don't need to. If you create a list of keys to the original hash in your required order:

    my @keysInPriorityOrder = sort { $data->{Elements}{$a}->{priority} <=> $data->{Elements}{$b}->{priority} } keys %{ $data->{Elements} };

    Then to process the sub hashes in that order:

    for my $key ( @keysInPriorityOrder ) { my $subhash = $data->{Elements}{ $key }; print $subhash->{ $_ } for qw[ Priority Name OtherVal ]; }

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
Re: Sorting on Nested Element
by TomDLux (Vicar) on Sep 30, 2011 at 18:34 UTC
    push @$sorted, $data->{Elements}{$_} for @pri;

    Some people recommend using curly braces with dual sigils. I certainly do that with more complicated ones, but I feels it's simple enough when you say, "Take this scalar and access the array ( or hash ) it references".

    As Occam said: Entia non sunt multiplicanda praeter necessitatem.

Re: Sorting on Nested Element
by Anonymous Monk on Sep 30, 2011 at 20:48 UTC

    Since keys are not needed:

    my $sorted = [ sort {$a->{Priority} <=> $b->{Priority}} values %{$data->{Elements}} ];

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://928852]
Approved by lidden
Front-paged by toolic
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others chanting in the Monastery: (8)
As of 2015-08-05 11:00 GMT
Find Nodes?
    Voting Booth?

    The oldest computer book still on my shelves (or on my digital media) is ...

    Results (81 votes), past polls