mirror of
https://github.com/ets-labs/python-dependency-injector.git
synced 2024-11-23 01:56:58 +03:00
108 lines
3.7 KiB
ReStructuredText
108 lines
3.7 KiB
ReStructuredText
Factory providers
|
|
-----------------
|
|
|
|
.. currentmodule:: dependency_injector.providers
|
|
|
|
:py:class:`Factory` provider creates new instance of specified class on every
|
|
call.
|
|
|
|
Nothing could be better than brief example:
|
|
|
|
.. image:: /images/providers/factory.png
|
|
:width: 80%
|
|
:align: center
|
|
|
|
.. literalinclude:: ../../examples/providers/factory.py
|
|
:language: python
|
|
:linenos:
|
|
|
|
Factory providers and __init__ injections
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
:py:class:`Factory` takes a various number of positional and keyword arguments
|
|
that are used as ``__init__()`` injections. Every time, when
|
|
:py:class:`Factory` creates new one instance, positional and keyword
|
|
argument injections would be passed as an instance's arguments.
|
|
|
|
Injections are done according to the next rules:
|
|
|
|
+ All providers (instances of :py:class:`Provider`) are called every time
|
|
when injection needs to be done.
|
|
+ Providers could be injected "as is" (delegated), if it is defined obviously.
|
|
Check out :ref:`factory_providers_delegation`.
|
|
+ All other injectable values are provided *"as is"*.
|
|
+ Positional context arguments will be appended after :py:class:`Factory`
|
|
positional injections.
|
|
+ Keyword context arguments have priority on :py:class:`Factory` keyword
|
|
injections and will be merged over them.
|
|
|
|
For example, if injectable value of injection is a :py:class:`Factory`, it
|
|
will provide new one instance (as a result of its call) every time, when
|
|
injection needs to be done.
|
|
|
|
Example below is a little bit more complicated. It shows how to create
|
|
:py:class:`Factory` of particular class with ``__init__()`` injections which
|
|
injectable values are also provided by another factories:
|
|
|
|
.. image:: /images/providers/factory_init_injections.png
|
|
|
|
.. literalinclude:: ../../examples/providers/factory_init_injections.py
|
|
:language: python
|
|
:linenos:
|
|
|
|
.. _factory_providers_delegation:
|
|
|
|
Factory providers delegation
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
:py:class:`Factory` provider could be delegated to any other provider via any
|
|
kind of injection.
|
|
|
|
As it was mentioned earlier, if :py:class:`Factory` is
|
|
injectable value, it will be called every time when injection needs to be
|
|
done. But sometimes there is a need to inject :py:class:`Factory` provider
|
|
itself (not a result of its call) as a dependency. Such injections are called
|
|
- *delegated provider injections*.
|
|
|
|
Saying in other words, delegation of factories - is a way to inject factories
|
|
themselves, instead of results of their calls.
|
|
|
|
:py:class:`Factory` delegation is performed by wrapping delegated
|
|
:py:class:`Factory` into special provider type - :py:class:`Delegate`, that
|
|
just returns wrapped :py:class:`Factory`.
|
|
|
|
Actually, there are three ways for creating factory delegates:
|
|
|
|
+ ``DelegatedFactory(...)`` - use special type of factory -
|
|
:py:class:`DelegatedFactory`. Such factories are always injected as
|
|
delegates ("as is").
|
|
+ ``Delegate(Factory(...))`` - obviously wrapping factory into
|
|
:py:class:`Delegate` provider.
|
|
+ ``Factory(...).delegate()`` - calling factory :py:meth:`Factory.delegate`
|
|
method, that returns delegate wrapper for current factory.
|
|
|
|
Example:
|
|
|
|
.. image:: /images/providers/factory_delegation.png
|
|
:width: 85%
|
|
:align: center
|
|
|
|
.. literalinclude:: ../../examples/providers/factory_delegation.py
|
|
:language: python
|
|
:linenos:
|
|
|
|
.. _factory_providers_specialization:
|
|
|
|
Factory providers specialization
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
:py:class:`Factory` provider could be specialized for any kind of needs via
|
|
creating its subclasses.
|
|
|
|
One of such specialization features is a limitation to :py:class:`Factory`
|
|
provided type:
|
|
|
|
.. literalinclude:: ../../examples/providers/factory_provided_type.py
|
|
:language: python
|
|
:linenos:
|