Hash

@jonmarkgo would Hash#diff work? #railsconf

# File activesupport/lib/active_support/json/encoding.rb, line 245 def encode_json (encoder ) # values are encoded with use_options = false, because we don't want hash representations from ActiveModel to be # processed once again with as_json with options, as this could cause unexpected results (i.e. missing fields); # on the other hand, we need to run as_json on the elements, because the model representation may contain fields # like Time/Date in their original (not jsonified) form, etc. "{#{map { |k,v| "#{encoder.encode(k.to_s)}:#{encoder.encode(v, false)}" } * ','}}"

Full article: http://api.rubyonrails.org/classes/Hash.html#method-i-diff