batch_processor.rb

class BatchItemProcessor
  attr_accessor :processed_items

  def initialize
    @processed_items = []
  end

  def process_items(list)
    list = list.select(&@condition) if @condition
    items = parse list
    items -= @processed_items
    @processed_items += items
    items.map { |item| yield item } unless items.empty?
  end

  def parse(items)
    items.map do |item|
      if item.is_a? Hash
        result = @id ? item[@id] : item[@id].object_id
      else
        result = item
      end
    end.compact
  end

  def identify(id)
    @id = id
  end

  def should_process(&block)
    @condition = block
  end

  def reset
    @processed_items = []
    @id = nil
    @condition = nil
  end
end