[LRUG] Sorting a hash by value

[Gabe da Silveira]

I agree with the general questioning of data structure since a hash is not
really intended to be ordered (and in fact wasn't until ruby 1.9), however
I understand the convenience of it, and if you really do need both the
ordered property *and* hash-like key lookup then consider reinitializing
the Hash from the sorted pairs:

Hash[*sorted_pairs.flatten]



On Tue, Jun 17, 2014 at 3:15 PM, Sam Livingston-Gray <geeksam at gmail.com>
wrote:

> Taking a cue from @JEG2, you could reverse it:
>
> catalogue.select {...}.map(&:reverse).sort.map(&:reverse)
>
> ...but (as already mentioned) #sort_by is much easier to read:
>
> catalogue.select {...}.sort_by(&:last)
>
> --
> (Sent from phone. Please excuse: brevity, top posting, hilarious
> autocorrections.)
>
> On Jun 17, 2014, at 3:46 AM, Stephen Nelson-Smith <sanelson at gmail.com>
> wrote:
>
> I have a hash that looks like this:
>
> {"ami-c3c73c7f"=>"tn-example 1980-09-12T17:53:25Z",
>  "ami-600925fe"=>"sns-example 1983-01-05T16:21:08Z",
>  "ami-131f1007"=>"dk-example 2005-01-27T23:03:01Z",
>  "ami-98d4ddef"=>"tn-example 2002-10-27T11:52:26Z",
>  "ami-fe6af742"=>"sns-example 1998-11-22T09:54:51Z",
>  "ami-09966e45"=>"dk-example 1993-01-09T13:23:45Z",
>  "ami-44e6ee6a"=>"tn-example 2013-12-23T20:52:28Z",
>  "ami-cbf7f1a9"=>"sns-example 1979-09-09T07:15:47Z",
>  "ami-fcd2e7ac"=>"dk-example 2007-09-02T18:34:05Z"}
>
> I want to filter this hash by value and return them in sorted date order.
>  The implementation I have just seems ugly:
>
> catalogue.select {|id, name| name.match /sns-example/ }.sort { |id, name|
> name[1] <=> id[1] }
> => [["ami-a65e21cc", "sns-example 2011-10-03T11:15:49Z"],
>  ["ami-9a401c41", "sns-example 1983-09-22T15:26:00Z"],
>  ["ami-9f9ae4d8", "sns-example 1971-03-06T03:58:52Z"]]
>
>
> I don't like the way sort takes my hash and makes it into an array of
> tuples... and I'd really like it to return an array of single key/value
> hashes...
>
> Also, is there a more elegant way to perform the filter/search?
>
> S.
>
> --
> Stephen Nelson-Smith
> Technical Director
> Atalanta Systems Ltd
> www.atalanta-systems.com
>
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