json.rb

# Convenience method for responding with JSON. Sets the content type,
# serializes, and allows empty responses. If json'ing an ActiveRecord object,
# and the object has errors on it, a 409 Conflict will be returned with a
# list of error messages.
def json(obj, status=200)
  obj = {} if obj.nil?
  if obj.respond_to?(:errors) && obj.errors.any?
    obj = {'errors' => obj.errors.full_messages}
    status = 409
  end
  render :json => obj, :status => status
end