dig.rb

class Hash

  def dig(*path)
    path.inject(self) do |location, key|
      location.is_a?(Hash) ? location[key] : nil
    end
  end

end

gistfile1.txt

1.9.3p0 :001 > h = {:foo => {:bar => {:baz => {:qux => true}}}}
 => {:foo=>{:bar=>{:baz=>{:qux=>true}}}} 

1.9.3p0 :002 > h.dig(:foo, :bar, :baz, :qux)
 => true 

1.9.3p0 :003 > h.dig(:foo, :bar, :baz, :qux, :barf)
 => nil 

1.9.3p0 :004 > h.dig(:foo, :bar)
 => {:baz=>{:qux=>true}} 

1.9.3p0 :005 > h.dig(:foo, :bar, :flapjacks)
 => nil