Flatten deep hash of attributes into readable keys and values.

make_one_dimensional.rb

def make_one_dimensional(input = {}, output = {}, prefix = nil)
  if input.respond_to?(:each)
    input.each do |key, value|
      key = [prefix, key].compact.join('.')
      case value
      when Hash
        make_one_dimensional(value, output, key)
      when Array
        value.each_with_index do |v, index|
          array_key = "#{key}[#{index}]"
          make_one_dimensional(v, output, array_key)
        end
      else
        output[key] = value
      end
    end
  else
    output[prefix] = input
  end
  output
end

spec.rb

require 'rspec'
require_relative 'make_one_dimensional'

describe 'make_one_dimensional' do
  let(:h) do
    {
      :a => {
        :b => [1, 2, 3],
        :c => [{:d => 4, :e => {:f => 5, :g => ['6', '6b']}}, {:h => 7}],
        :i => '8'
      },
      :j => 9
    }
  end

  it "should flatten" do
    make_one_dimensional(h).should == {
      'a.b[0]' => 1,
      'a.b[1]' => 2,
      'a.b[2]' => 3,
      'a.c[0].d' => 4,
      'a.c[0].e.f' => 5,
      'a.c[0].e.g[0]' => '6',
      'a.c[0].e.g[1]' => '6b',
      'a.c[1].h' => 7,
      'a.i' => '8',
      'j' => 9
    }
  end
end