48 lines
1.7 KiB
ReStructuredText
48 lines
1.7 KiB
ReStructuredText
.. _faq:
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Frequently Asked Questions
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==========================
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If I use :func:`~injector.inject` or scope decorators on my classess will I be able to create instances of them without using Injector?
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---------------------------------------------------------------------------------------------------------------------------------------
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Yes. Scope decorators don't change the way you can construct your class
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instances without Injector interaction.
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I'm calling this method (/function/class) but I'm getting "TypeError: XXX() takes exactly X arguments (Y given)"
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----------------------------------------------------------------------------------------------------------------
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Example code:
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.. code-block:: python
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class X:
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@inject
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def __init__(self, s: str):
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self.s = s
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def configure(binder):
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binder.bind(s, to='some string')
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injector = Injector(configure)
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x = X()
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Result?
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::
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TypeError: __init__() takes exactly 2 arguments (1 given)
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Reason? There's *no* global state that :class:`Injector` modifies when
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it's instantiated and configured. Its whole knowledge about bindings etc.
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is stored in itself. Moreover :func:`inject` will *not* make
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dependencies appear out of thin air when you for example attempt to create
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an instance of a class manually (without ``Injector``'s help) - there's no
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global state ``@inject`` decorated methods can access.
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In order for ``X`` to be able to use bindings defined in ``@inject``
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decoration :class:`Injector` needs to be used (directly or indirectly)
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to create an instance of ``X``. This means most of the time you want to just
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inject ``X`` where you need it, you can also use :meth:`Injector.get` to obtain
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an instance of the class (see its documentation for usage notes).
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