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

I couldn't use other suggestions here directly, but it got me on the right track.

With Rails 5.2, using a versioned API and thus unable to change it for the whole application. I created this concern which i then included into the base controller of my new api version module.

module UnderscoreizeParams
  extend ActiveSupport::Concern

  def process_action(*args)
    request.parameters.deep_transform_keys!(&:underscore)
    super
  end
end

then in my API V3 BaseController

class V3::BaseController
  include UnderscoreizeParams
end

enjoy.

Answer 2

We are converting our Rails API JSON keys from snake_case to camelCase. We have to do the conversion incrementally, i.e. some APIs work with snake_case while the others change to using camelCase.

Our solution is that we

• create method ActionController::Parameters#deep_snakeize
• create method ApplicationController#snakeize_params
• set before_action :snakeize_params only for the controller actions that handle incoming request with camelCase keys

You can try vochicong/rails-json-api for a fully working Rails app example.

# File: config/initializers/params_snakeizer.rb
# Transform JSON request param keys from JSON-conventional camelCase to
# Rails-conventional snake_case
module ActionController
  # Modified from action_controller/metal/strong_parameters.rb
  class Parameters
    def deep_snakeize!
      @parameters.deep_transform_keys!(&:underscore)
      self
    end
  end
end

# File: app/controllers/application_controller.rb
class ApplicationController < ActionController::API
  protected

    # Snakeize JSON API request params
    def snakeize_params
      params.deep_snakeize!
    end
end

class UsersController < ApplicationController
  before_action :snakeize_params, only: [:create]

  # POST /users
  def create
    @user = User.new(user_params)

    if @user.save
      render :show, status: :created, location: @user
    else
      render json: @user.errors, status: :unprocessable_entity
    end
  end
end