Hash decoration with custom method for finding value for any nested key

hash_ext.rb

require 'rspec'

RSpec.configure do |config|
  config.mock_with :rspec
  config.color_enabled = true
end

module MyHashTools

  def get_val_for(sym)
    if self[sym]
      final = self[sym]
    else
      self.each do |(k, v)|
        if v.class == Hash && !v.respond_to?(:get_val_for)
          v.extend(MyHashTools)
          final = v.get_val_for(sym)
        end
      end
    end
    final
  end

end

describe Hash do
  subject do
    {:a => 3, :b => {:c => 5, :d => {:e => 7}}}
  end

  context "when my hash responds to get_val_for" do
    before do
      subject.extend(MyHashTools)
    end

    it "returns the value for the key" do
      subject.get_val_for(:e).should eq(7)
    end
  end

  context "when my hash does not respond to get_val_for" do
    it "raises an error" do
      expect { subject.get_val_for(:e) }.to raise_exception(NoMethodError)
    end
  end
end