From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-01-26T03:16:44+09:00
Subject: Re: Nested hash with arrays for default value

On Mon, Jan 25, 2010 at 6:48 PM, Glen Holcomb <damnbigman@gmail.com> wrote:
> I'm trying to find a "nice" way to make a nested hash with an empty array as
> the default "leaf" value.
>
> Basically I'd like to be able to make an assignment as follows:
>
>    data[2][3][4][5] << 3
>
> I can get close but I can't get it right.  The data is going to be coming
> straight out of a log so I can't really build the hash ahead of time.
>
> --
> "Hey brother Christian with your high and mighty errand, Your actions speak
> so loud, I can’t hear a word you’re saying."
>
> -Greg Graffin (Bad Religion)
>

I've not tested this too much, but what I tried was to setup a proxy
object that would insert a hash if the [] method is called on it, or
an array if the << method was called:

class ProxyDefault
	def initialize hash, key
		@hash = hash
		@key = key
	end
	
	def [](key)
		@hash[@key] = Hash.new {|hash,key| ProxyDefault.new(hash, key)}
		@hash[@key][key]
	end
	
	def << value
		@hash[@key] = []
		@hash[@key] << value
	end
end
		
h = Hash.new {|hash,value| ProxyDefault.new(hash, value)}

h[1][2][3] << "value"

p h
p h[1][2][3]

/temp$ ruby nested_hash_array.rb
{1=>{2=>{3=>["value"]}}}
["value"]

Hope this helps,

Jesus.