Reply to https://medium.com/@galaspiotrek/i-like-your-approach-d51f7046d295

params_slicer.rb

class ParamsSlicer
  def initialize(params, *whitelist)
    @params = params
    @nested_whitelist = whitelist.extract_options!
    @whitelist = whitelist
  end

  def call
    params.slice(*whitelist).tap do |result|
      nested_whitelist.each do |k, v|
        result[k] = params[k].slice(*v)
      end
    end
  end
  
  private

  attr_reader :params, :nested_whitelist, :whitelist
end

h = {name: 'Mike', address_attributes: {city: 'Berlin', street: 'lisenhof'}}

ParamsSlicer.new(h, :name, address_attributes: %i[city]).call