74 lines
2.3 KiB
ReStructuredText
74 lines
2.3 KiB
ReStructuredText
|
Writing custom providers
|
||
|
|
------------------------
|
||
|
|
|
||
|
|
List of *Objects* providers could be widened with custom providers.
|
||
|
|
|
||
|
|
Below are some tips and recommendations that have to be met:
|
||
|
|
|
||
|
|
1. Every custom provider has to extend base provider class -
|
||
|
|
``objects.providers.Provider``.
|
||
|
|
2. Cusom provider's ``__init__()`` could be overriden with only condition:
|
||
|
|
parent initializer (``objects.providers.Provider.__init__()``) has
|
||
|
|
to be called.
|
||
|
|
3. Providing strategy has to be implemented in custom provider's
|
||
|
|
``_provide()`` method. All ``*args`` & ``**kwargs`` that will be
|
||
|
|
recieved by ``objects.providers.Provider.__call__()`` will be transefed
|
||
|
|
to custom provider's ``_provide()``.
|
||
|
|
4. If custom provider is based on some standard providers, it is better to
|
||
|
|
use delegation of standard providers, then extending of them.
|
||
|
|
5. If custom provider defines any attributes, it is good to list them in
|
||
|
|
``__slots__`` attribute (as *Objects* does). It can save some memory.
|
||
|
|
6. If custom provider deals with injections (e.g. ``Factory``,
|
||
|
|
``Singleton`` providers), it is strongly recommended to use
|
||
|
|
``objects.injections.Injection`` and its subclasses:
|
||
|
|
``objects.injections.KwArg``, ``objects.injections.Attribute`` and
|
||
|
|
``objects.injections.Method``.
|
||
|
|
|
||
|
|
Example:
|
||
|
|
|
||
|
|
.. image:: /images/providers/custom_provider.png
|
||
|
|
:width: 100%
|
||
|
|
:align: center
|
||
|
|
|
||
|
|
.. code-block:: python
|
||
|
|
|
||
|
|
"""Custom `Factory` example."""
|
||
|
|
|
||
|
|
from objects.providers import Provider
|
||
|
|
from objects.providers import Factory
|
||
|
|
|
||
|
|
|
||
|
|
class User(object):
|
||
|
|
|
||
|
|
"""Example class User."""
|
||
|
|
|
||
|
|
|
||
|
|
class UsersFactory(Provider):
|
||
|
|
|
||
|
|
"""Example users factory."""
|
||
|
|
|
||
|
|
__slots__ = ('_factory',)
|
||
|
|
|
||
|
|
def __init__(self):
|
||
|
|
"""Initializer."""
|
||
|
|
self._factory = Factory(User)
|
||
|
|
super(UsersFactory, self).__init__()
|
||
|
|
|
||
|
|
def _provide(self, *args, **kwargs):
|
||
|
|
"""Return provided instance."""
|
||
|
|
return self._factory(*args, **kwargs)
|
||
|
|
|
||
|
|
|
||
|
|
# Users factory:
|
||
|
|
users_factory = UsersFactory()
|
||
|
|
|
||
|
|
# Creating several User objects:
|
||
|
|
user1 = users_factory()
|
||
|
|
user2 = users_factory()
|
||
|
|
|
||
|
|
# Making some asserts:
|
||
|
|
assert isinstance(user1, User)
|
||
|
|
assert isinstance(user2, User)
|
||
|
|
assert user1 is not user2
|
||
|
|
|