1_example_usage.rb

class Foo
  extend AutoCoercions
  
  coerce :date_gte, :date_lte, with: :to_date
  coerce :trip_mode_eq, :trip_purpose_eq, :trip_count_gte, with: :to_i
  coerce :select_random_winners, with: ->(v) { v == '1' }
  coerce :random_winner_count, with: :to_i

  def initialize(attributes = {})
    @attributes = self.class.apply_coercions(attributes)
  end

end

2_auto_coercions.rb

module AutoCoercions

  def coercions
    @coercions ||= {}.with_indifferent_access
  end

  def custom_coercions
    @custom_coercions ||= {}.with_indifferent_access.tap do |custom_coercions|
      custom_coercions[:to_date] = ->(value) do
        if Date._parse(value, false).keys == [:year, :mon, :mday]
          value.to_date
        end
      end
    end
  end

  def coerce(*args)
    options = args.extract_options!
    with = options[:with]

    args.each do |method|
      if with.respond_to?(:call)
        coercions[method] = with
      elsif custom_coercions[with]
        coercions[method] = custom_coercions[with]
      else
        coercions[method] = ->(value) { value.send(with) }
      end
    end
  end

  def apply_coercions(attributes)
    identity = ->(x) { x }

    Hash[
      attributes.map { |key, value|
        with = coercions.fetch(key, identity)
        [key, value.present? ? with.call(value) : nil]
      }
    ]
  end
end