nested_flatten.rb

# silly but useful. 
# -> compresses nested hashes into dot separated key value pairs

class Hash
  def nested_flatten(prefix = 'h')
    arr = []

    each do |key, value|
      k = prefix + ".#{key}"

      if value.is_a? Hash
        arr += value.nested_flatten(k)
      elsif value.is_a? Array
        arr += value.map {|v| [k, v]}
      else
        arr.push [k, value]
      end

    end
    arr
  end
end

if $0 == __FILE__
  require 'rubygems'
  require 'spec/autorun'

  describe Hash do
    it "should flatten simple hash" do
      h = {1 => 2}.nested_flatten('pr')
      h.size.should == 1

      h.first[0].should == "pr.1"
      h.first[1].should == 2
    end

    it "should accepted nested hashes" do
      h = {1 => {2 => 3, 4 => 5}, 6 => 7}.nested_flatten('pr')
      h.size.should == 3

      h.flatten.include? "pr.1.2"
      h.flatten.include? "pr.1.4"
      h.flatten.include? "pr.6"
    end

    it "should accept nested arrays" do
      h = {1 => [2,3,4]}.nested_flatten('pr')
      h.size.should == 3
    end
  end
end