Callable providers
------------------

``Callable`` provider is a provider that wraps particular callable with
some injections. Every call of this provider returns result of call of initial
callable.

``Callable`` provider uses ``KwArg`` injections. ``KwArg`` injections are
done by passing injectable values as keyword arguments during call time.

Context keyword arguments have higher priority than ``KwArg`` injections.

Example:

.. image:: /images/callable.png
    :width: 100%
    :align: center

.. code-block:: python

    """`Callable` providers example."""

    from passlib.hash import sha256_crypt

    from objects.providers import Callable
    from objects.injections import KwArg


    # Password hasher and verifier providers (hash function could be changed
    # anytime (for example, to sha512) without any changes in client's code):
    password_hasher = Callable(sha256_crypt.encrypt,
                               KwArg('salt_size', 16),
                               KwArg('rounds', 10000))
    password_verifier = Callable(sha256_crypt.verify)

    # Making some asserts (client's code):
    hashed_password = password_hasher('super secret')
    assert password_verifier('super secret', hashed_password)