Food-based subscription examples

This file gives more subscription examples using a cooking-based example:

>>> from zope.interface.adapter import AdapterRegistry
>>> registry = AdapterRegistry()

>>> import zope.interface
>>> class IAnimal(zope.interface.Interface):
...     pass
>>> class IPoultry(IAnimal):
...     pass
>>> class IChicken(IPoultry):
...     pass
>>> class ISeafood(IAnimal):
...     pass

Adapting to some other interface for which there is no subscription adapter returns an empty sequence:

>>> class IRecipe(zope.interface.Interface):
...     pass
>>> class ISausages(IRecipe):
...     pass
>>> class INoodles(IRecipe):
...     pass
>>> class IKFC(IRecipe):
...     pass

>>> list(registry.subscriptions([IPoultry], IRecipe))
[]

unless we define a subscription:

>>> registry.subscribe([IAnimal], ISausages, 'sausages')
>>> list(registry.subscriptions([IPoultry], ISausages))
['sausages']

And define another subscription adapter:

>>> registry.subscribe([IPoultry], INoodles, 'noodles')
>>> meals = list(registry.subscriptions([IPoultry], IRecipe))
>>> meals.sort()
>>> meals
['noodles', 'sausages']

>>> registry.subscribe([IChicken], IKFC, 'kfc')
>>> meals = list(registry.subscriptions([IChicken], IRecipe))
>>> meals.sort()
>>> meals
['kfc', 'noodles', 'sausages']

And the answer for poultry hasn't changed:

>>> meals = list(registry.subscriptions([IPoultry], IRecipe))
>>> meals.sort()
>>> meals
['noodles', 'sausages']