iterator.rb

class SystemLogger
  def initialize
    @sys_logs = []
  end

  def add(msg)
    timestamp = Time.now.strftime('%Y%m%d_%H%M%S_%N')
    @sys_logs << [timestamp, msg]
  end

  def logs
    @sys_logs
  end

  def create_iterator
    SystemLoggerIterator.new(logs)
  end

  class SystemLoggerIterator

    def initialize(sys_logs)
      @items = sys_logs
      @size = @items.size
      @position = 0
    end

    def has_next?
      @position < @size
    end

    def next
      return nil unless has_next?
      item = @items[@position].last
      @position += 1
      item
    end
  end
end

class ApplicationLogger
  def initialize
    @app_logs = {}
  end

  def add(msg)
    timestamp = Time.now.strftime('%Y%m%d_%H%M%S_%N')
    @app_logs[timestamp] = msg
  end

  def logs
    @app_logs
  end

  def create_iterator
    ApplicationLoggerIterator.new(logs)
  end

  class ApplicationLoggerIterator

    def initialize(app_logs)
      @items = app_logs.values
      @size = @items.size
      @position = 0
    end

    def has_next?
      @position < @size
    end

    def next
      return nil unless has_next?
      item = @items[@position]
      @position += 1
      item
    end
  end
end

class LogCollector
  def initialize(loggers)
    @loggers = loggers
  end

  def collect
    all_logs = []
    @loggers.each do |logger|
      iterator = logger.create_iterator
      while iterator.has_next?
        all_logs << iterator.next
      end
    end
    all_logs
  end
end

sys_logger = SystemLogger.new
sys_logger.add('Segmentation fault.')
sys_logger.add('The server is on fire.')
sys_logger.add('yoyoyo')


app_logger = ApplicationLogger.new
app_logger.add('This is a pen, this is an apple.')
app_logger.add('Kait is not a cat.')
app_logger.add('WebTechTopic is awesome.')


log_collector = LogCollector.new([sys_logger, app_logger])
p log_collector.collect