From: Clifford Heath <no@...>
Date: 2011-04-14T08:40:34+09:00
Subject: Re: Help on hashing multiple keys and values

On 04/14/11 09:33, Adam Adam wrote:
> I'm trying to create a hash with multiple values per key from a tab
> delimited file. numbers_and_colors.txt example:
>
> 1    Red
> 2    Blue
> 3    Red
> 2    Green
>
> What I need is a hash that has key 2 assigned to values Blue and Green.
> Running what I have below just erases the previous key, so puts
> name_hash["2"] would only show Green. Ruby example:
>
> name_hash = Hash.new
> File.open("numbers_and_colors.txt").each do |file_line|
>    file_line.chomp!
>    line_parts = file_line.split(/\t/)
>    name_hash["#{line_parts[0]}"] = "#{line_parts[1]}"
>
> I need this in a hash, so is there another way to go about this? Thanks
> in advance to any help, as you can probable tell I only started learning
> Ruby recently.

The idiom I use is to add an array to hold the values, like this:

(name_hash[key] ||= []) << value

Clifford Heath.