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