38 lines
1.6 KiB
ReStructuredText
38 lines
1.6 KiB
ReStructuredText
Writing custom providers
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------------------------
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List of *Dependency Injector* providers could be widened with custom providers.
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Below are some tips and recommendations that have to be met:
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1. Every custom provider has to extend base provider class -
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``dependency_injector.providers.Provider``.
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2. Cusom provider's ``__init__()`` could be overriden with only condition:
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parent initializer
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(``dependency_injector.providers.Provider.__init__()``) has to be called.
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3. Providing strategy has to be implemented in custom provider's
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``_provide()`` method. All ``*args`` & ``**kwargs`` that will be
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recieved by ``dependency_injector.providers.Provider.__call__()`` will be
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transefed
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to custom provider's ``_provide()``.
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4. If custom provider is based on some standard providers, it is better to
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use delegation of standard providers, then extending of them.
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5. If custom provider defines any attributes, it is good to list them in
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``__slots__`` attribute (as *Dependency Injector* does). It can save
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some memory.
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6. If custom provider deals with injections (e.g. ``Factory``,
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``Singleton`` providers), it is strongly recommended to use
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``dependency_injector.injections.Injection`` and its subclasses:
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``dependency_injector.injections.KwArg``,
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``dependency_injector.injections.Attribute`` and
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``dependency_injector.injections.Method``.
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Example:
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.. image:: /images/providers/custom_provider.png
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:width: 100%
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:align: center
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.. literalinclude:: ../../examples/providers/custom_factory.py
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:language: python
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