"""This mixin supports autoloading."""
__docformat__ = "restructuredtext"
class AutoLoader:
"""This mixin supports autoloading.
That means if you try to access an undefined attribute (e.g.
``self.Spam``), an aquarium.util.AquariumClass_ instance which uses this
mixin will automatically import and instantiate the AquariumClass called
``Spam`` that is the same type of module as it is (e.g. a database module
instance would try to import and instantiate ``aquarium.database.Spam``).
This mixin is used by aquarium.database.DatabaseAssistant_, etc.
.. _aquarium.util.AquariumClass:
aquarium.util.AquariumClass.AquariumClass-class.html
.. _aquarium.database.DatabaseAssistant:
aquarium.database.DatabaseAssistant.DatabaseAssistant-class.html
"""
def __getattr__(self, attr):
"""Import, instantiate, and return the desired instance.
Note, these instances will be cached in ``self._autoLoaderCache``.
"""
if not self.__dict__.has_key("_autoLoaderCache"):
self._autoLoaderCache = {}
cache = self._autoLoaderCache
if not cache.has_key(attr):
try:
cache[attr] = self._ctx.iLib.aquariumFactory("%s.%s" %
(self.getModuleType(), attr))
except ImportError:
raise AttributeError("""\
%s instance has no attribute '%s', and AutoLoader failed too""" %
(self.__class__.__name__, attr))
return cache[attr]
def getModuleType(self):
"""Return the type of Aquarium module this instance is.
Usually, I can automatically figure out what type of module you are,
but if you need to get fancy, override this.
"""
# If "self.__module__" yields something like "aquarium.screen.Screen",
# the goal is to return "screen".
return self.__module__.split(".")[1:-1]
