Enums

Since Enum definition keep enumeration itself a class we need to instantiate it somehow. Even taking into consideration that enumeration classes are used as constants most of the times, we can't make an exclusion in the rule that classes should be instantiated. Members of enumeration are instancies of the enumeration class itself. That's why we allow to use Enum members only in the dependency injection scope.

>>> from enum import Enum, auto, unique
>>> from dependencies import Injector

>>> @unique
... class Status(Enum):
...     new = auto()
...     accepted = auto()
...     processed = auto()
...     rejected = auto()
...     done = auto()

>>> class Order:
...     def __init__(self, status):
...         self.status = status
...
...     def __repr__(self):
...         return f"Order({self.status!r})"

>>> class Container(Injector):
...     order = Order
...     status = Status.new

>>> Container.order
Order(<Status.new: 1>)

In the mean time, we are strongly forbid usage Enum class itself inside injection scope. Injector will raise an error if you try to define an attribute with enumeration class in it.

>>> class Container(Injector):
...     order = Order
...     status = Status

>>> Container.order
Traceback (most recent call last):
  ...
_dependencies.exceptions.DependencyError: Attribute 'status' contains Enum.
<BLANKLINE>
Do not inject enumeration classes.
<BLANKLINE>
It will be unable to instantiate this class.
<BLANKLINE>
Inject its members instead.

Using enumeration classes in class-named attributes are still allowed.

>>> class Price:
...     def __init__(self, status_class):
...         self.status_class = status_class
...
...     def __repr__(self):
...         return f"Price({self.status_class!r})"

>>> class Container(Injector):
...     price = Price
...     status_class = Status

>>> Container.price
Price(<enum 'Status'>)

As you can see, no exception was raised above.

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