如何组织此代码？

Question

我试图通过将函数转换为方法来将函数分类到适当的类中（如果合适，可以将函数留在类之外）。 但我不确定如何处理这个特定的功能（如下所示）。

首先，这是我的课：

class OreBlobAction:
   def __init__(self, entity, image_store):
      self.entity = entity
      self.image_store = image_store

   def ore_blob_action(self, world, action, ticks):
      entity = self.entity
      entity_pt = entities.get_position(self.entity)
      vein = find_nearest(world, entity_pt, entities.Vein)
      (tiles, found) = blob_to_vein(world, self.entity, vein)

      next_time = ticks + entities.get_rate(entity)
      if found:
         quake = create_quake(world, tiles[0], ticks, self.image_store)
         worldmodel.add_entity(world, quake)
         next_time = ticks + entities.get_rate(entity) * 2

      schedule_action(world, self.entity,
         OreBlobAction(self.entity, self.image_store), next_time)

      return tiles

现在，这是函数：

def take_action(world, action, ticks):
   entities.remove_pending_action(action.entity, action)
   if isinstance(action, VeinAction):
      return vein_action(world, action, ticks)
   elif isinstance(action, MinerNotFullAction):
      return miner_not_full_action(world, action, ticks)
   elif isinstance(action, MinerFullAction):
      return miner_full_action(world, action, ticks)
   elif isinstance(action, OreBlobAction):
      return ore_blob_action(world, action, ticks)
   elif isinstance(action, OreTransformAction):
      return ore_transform_action(world, action, ticks)
   elif isinstance(action, EntityDeathAction):
      return entity_death_action(world, action, ticks)
   elif isinstance(action, WyvernSpawnAction):
      return wyvern_spawn_action(world, action, ticks)
   elif isinstance(action, WyvernAction):
      return wyvern_action(world, action, ticks)
   elif isinstance(action, VeinSpawnAction):
      return vein_spawn_action(world, action, ticks)
   elif isinstance(action, AnimationAction):
      return animation_action(world, action, ticks)

   return []

如您所见，此函数不仅考虑了 OreBlobAction 类的操作，还考虑了多个其他类的操作。 将此函数留在 OreBlobAction 类之外会更好吗？ 或者有没有更好的方法来做到这一点？

注意：如果我将此函数排除在 OreBlobAction 类之外，并尝试运行该程序，则会出现以下错误：

NameError: global name 'ore_blob_action' is not defined

Answer 1

你关于动作类型的大 switch 语句是重构的危险信号。 有什么可以阻止您将“采取行动”方法转移到行动类本身中吗？ 例如

class Action(object):
    """ An action that can be performed on the game world. """

    def perform(self, world, ticks):
        """ Perform the action. """
        raise NotImplementedError()

这将是您的基本操作类，然后在每种类型的操作中，您将覆盖perform(...)方法，例如

class WyvernSpawnAction(Action):
    """ An action that spawns a Wyvern. """

    [... Some action specific initialisation code here ...]

    def perform(self, world, ticks):
        """ Spawn a Wyvern. """
        world.spawn(Wyvern(...))

从世界中删除动作的样板将保留，您现在可以自由添加新类型的动作，而无需最终在您的函数中添加数百个比较。 此外，您现在可以处理操作可以继承其他操作的行为的情况，而不必非常小心比较的顺序。