python-dependency-injector/docs/providers/dependency.rst

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Dependency provider
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===================
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.. currentmodule:: dependency_injector.providers
:py:class:`Dependency` provider is a placeholder for a dependency of a certain type.
To specify a type of the dependency use ``instance_of`` argument: ``Dependency(instance_of=SomeClass)``.
Dependency provider will control that returned object is an instance of ``instance_of`` type.
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.. literalinclude:: ../../examples/providers/dependency.py
:language: python
:lines: 3-
:emphasize-lines: 26,35-36
To provide a dependency you need to override the ``Dependency`` provider. You can call
provider ``.override()`` method or provide an overriding provider when creating a container.
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See :ref:`provider-overriding`. If you don't provide a dependency, ``Dependency`` provider
will raise an error:
.. literalinclude:: ../../examples/providers/dependency_undefined_error.py
:language: python
:lines: 18-
You also can provide a default for the dependency. To provide a default use ``default`` argument:
``Dependency(..., default=...)``. Default can be a value or a provider. If default is not a provider,
dependency provider will wrap it into the ``Object`` provider.
.. literalinclude:: ../../examples/providers/dependency_default.py
:language: python
:lines: 16-23
:emphasize-lines: 3
.. disqus::