From: Wes Bailey <wes@...>
Date: 2010-06-11T14:22:23+09:00
Subject: Re: Split an array of object by first letter

----- "Phrogz" <phrogz@mac.com> wrote:

> On Jun 10, 1:45 pm, Joel VanderWerf <joelvanderw...@gmail.com> wrote:
> > > I have an array of brands and I need to split this array by brand
> name
> > > first letter. How can I do that?
> >
> > ["fz", "yt", "fu", "za", "zw", "yo", "zb"].group_by {|s|s[0,1]}
> > => {"y"=>["yt", "yo"], "z"=>["za", "zw", "zb"], "f"=>["fz", "fu"]}
> 
> Joel is right on. My addition below shows that (a) this works not
> just
> for two-letter words, and (b) if you're using Ruby 1.9, you can use a
> slightly simpler syntax:
> 
> 
> [ "foo", "bar", "flim", "bork", "cow" ].group_by{ |name| name[0] }
> #=> {"f"=>["foo", "flim"], "b"=>["bar", "bork"], "c"=>["cow"]}
> 
> Note that case matters, but you can make it irrelevant:
> 
> [ "foo", "bar", "Flim", "bork" ].group_by{ |name| name[0] }
> #=> {"f"=>["foo"], "b"=>["bar", "bork"], "F"=>["Flim"]}
> 
> [ "foo", "bar", "Flim", "bork" ].group_by{ |name| name[0].downcase }
> #=> {"f"=>["foo", "Flim"], "b"=>["bar", "bork"]}
> 
> And finally, just for the love of monkeypatching:
> 
> class String
>   def first_letter
>     self[0].downcase
>   end
> end
> 
> class Array
>   def alphabetical
>     Hash[ group_by{|s|s.first_letter}.sort_by{|c,a|c} ]
>   end
> end
> 
> [ "foo", "bar", "Flim", "bork" ].alphabetical
> #=> {"b"=>["bar", "bork"], "f"=>["foo", "Flim"]}

Anyone remember %w or do you all love quotes so much :P

Since the poster didn't specify whether they were on ruby 1.8 or 1.9:

irb(main):021:0> %w/foo bar Film bork Baz/.inject( {} ) { |h,v| k = v[0,1].downcase; a = h[k] || []; h.merge( { k => a << v } ) }
=> {"b"=>["bar", "bork", "Baz"], "f"=>["foo", "Film"]}