14 December 2014

Automatic snake_case <=> lowerCamelCase with ActiveModel Serializer

Setup

Add active_model_serializers to your Gemfile, run bundle, of course.

Serializing

In ApplicationController:

# Disable the root node, eg: {projects: [{..}, {..}]}
def default_serializer_options
  {root: false}
end

Then in config/initializers/active_model_serializer.rb:

# Convert attributes from snake_case to lowerCamelCase
ActiveModel::Serializer.setup do |config|
  config.key_format = :lower_camel
end

Deserializing

Again in ApplicationController:

# Convert lowerCamelCase params to snake_case automatically
before_filter :deep_snake_case_params!
def deep_snake_case_params!(val = params)
  case val
  when Array
    val.map {|v| deep_snake_case_params! v }
  when Hash
    val.keys.each do |k, v = val[k]|
      val.delete k
      val[k.underscore] = deep_snake_case_params!(v)
    end
    val
  else
    val
  end
end

And you're done!

Go ahead and write your serializers and notice that they will output JSON like {fullName: 'Brent Vatne'}, and if you submit that same data back to Rails, it will automatically convert it to {full_name: 'Brent Vatne'}.