From: Siep Korteling <s.korteling@...>
Date: 2009-10-31T07:59:14+09:00
Subject: Re: two stage array sorting

John W Higgins wrote:
> Morning Tim,
> 
> On Fri, Oct 30, 2009 at 9:35 AM, Tim Ferrell <s0nspark@gmail.com> wrote:
> 
>> do this without resorting to a two stage process? Currently I am
>> breaking the array out into arrays by day and sorting those by time and
>> then reassembling... it just feels dirty :-)
>>
>>
> require 'date'
> 
> def sort_datetime_array(ary)
>   fmt = '%A %I:%M %p'
>   ary.sort{ |a,b|
>     DateTime.strptime(a, fmt) <=> DateTime.strptime(b, fmt)
>   }
> end
> 
> c = ['Friday 1:00 PM', 'Tuesday 12:00 AM', 'Wednesday 3:00 PM', 'Tuesday
> 11:59 PM']
> puts sort_datetime_array(c)
> 
> --output--
> Tuesday 12:00 AM
> Tuesday 11:59 PM
> Wednesday 3:00 PM
> Friday 1:00 PM
> 
> 
> Just note that the original array is not sorted in this case - the 
> method
> returns a new sorted array - if you wanted the sorting done in place 
> then
> change sort to sort! in the method 
> 
> John

In this case, sort_by is faster because it creates less DateTime 
objects.

def sort_by_datetime(ary)
  ary.sort_by {|el| Date.strptime(el, '%A %I:%M %p') }
end

(see the ri for enumerable#sort_by ).

Hth,

Siep


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