What is the best way to convert all controller params from camelCase to snake_case in Rails?

Question

As you already know, JSON naming convention advocates the use of camelSpace and the Rails advocates the use of snake_case for parameter names.

What is the best way t

Answer 1

Another rails 5.1 solution that piggy backs off of the Sebastian Hoitz solution above. To clarify why we need to do this: in R5.1 deep_transform_keys! is no longer a method available to us, since params are no longer inheriting from HashWithIndifferentAccess. And overcomes the issue mentioned by Eliot Sykes where the initializer only works for application/json mime types. It does add overhead to all the requests though. (I'd love to see some initializers for ActionDispatch::Request.parameter_parsers[:multipart_form]) though, since the initializer is a better place to be doing this, IMO.

before_action :normalize_key!

 def normalize_keys!(val = params)
  if val.class == Array
    val.map { |v| normalize_keys! v }
  else
    if val.respond_to?(:keys)
      val.keys.each do |k|
        current_key_value = val[k]
        val.delete k
        val[k.to_s.underscore] = normalize_keys!(current_key_value)
      end
    end
    val
  end
  val
end