From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2011-02-03T00:37:20+09:00
Subject: Re: Soliciting some help with inject method

On Wed, Feb 2, 2011 at 3:56 PM, Edmond Kachale
<edmond.kachale@baobabhealth.org> wrote:
> Rubysters,
>
> I think I am not wrong if I can solicit some knowledge. :-)
>
> Can any one help modify this code?
>
> I have:
> array = [['a', 1], ['b', 2], ['a',2], ['c',4], ['d', 5], ['b',4]]
>
> I want to create a hash using inject method:
>>> hash = {'a' => [1, 2], 'b' => [2, 4], 'c' => [4], 'd' => [5]}
>
> The following code gives: {"a"=>[2], "b"=>[4], "c"=>[4], "d"=>[5]}
>
> hash  = array.inject({}) do |result, array|
> new_hash = {}
> new_hash[array.first] = [array.last]
> result.merge!(new_hash)  # I have tried result.update(new_hash) but it fails
> too
> result
> end
>
> Here is a console friendly version of the same:
> hash  = array.inject({}){|result, array| new_hash = {};
> new_hash[array.first] = [array.last]; result.merge!(new_hash); result;}
>
> Thanks in advance,

Yet another way without inject:

irb(main):001:0> array = [['a', 1], ['b', 2], ['a',2], ['c',4], ['d',
5], ['b',4]]
=> [["a", 1], ["b", 2], ["a", 2], ["c", 4], ["d", 5], ["b", 4]]
irb(main):002:0> result = Hash.new {|h,k| h[k] = []}
=> {}
irb(main):003:0> array.each {|key,value| result[key] << value}
=> [["a", 1], ["b", 2], ["a", 2], ["c", 4], ["d", 5], ["b", 4]]
irb(main):004:0> result
=> {"a"=>[1, 2], "b"=>[2, 4], "c"=>[4], "d"=>[5]}

Jesus.