Action Chunking

Bad code:

thread do
  worker = Worker.new
  for x = 0 to max
    worker.do_item(x)
  end
end

Good code:

worker = Worker.new
timer do
  if worker.fetch_next_item
    worker.do_current_item
  else
    stop_timer
  end
end

The latter is an example of ActionChunking. The worker object is more EventDriven. It maintains its own current index, and does not rely on an external loop statement to maintain its current state.

To avoid PrematureConcurrency, if you think you must thread, always try action chunking first (or try selecting from an array of mutex semaphores!). If you then prove you need a thread (per ConcurrencyVsXp), you will probably be better off using the action-chunked version of the design:

thread do
  worker = Worker.new
  while worker.index < worker.max
    worker.do_current_item
  end
end

One common (bad) tutorial example of threading is hiding a long process from a GUI. In many situations, the ActionChunked version is more flexible, using the GUI's timer facility for its pump. Such a process is very easy to upgrade with a

• cancel button
• progress bar
• restart button
• realtime log or transcript
• exception handler.