Declarative catalogs
--------------------

:py:class:`dependency_injector.catalogs.DeclarativeCatalog` is a catalog of 
providers that could be defined in declarative manner. It should cover most 
of the cases when list of providers that would be included in catalog is 
deterministic (catalog will not change its structure in runtime).

Declarative catalogs have to extend base declarative catalog class - 
:py:class:`dependency_injector.catalogs.DeclarativeCatalog`.

Providers have to be defined like catalog's class attributes. Every provider in
catalog has name. This name should follow ``some_provider`` convention, 
that is standard naming convention for attribute names in Python.

.. note::

    It might be useful to add such 
    ``""":type: dependency_injector.providers.Provider -> Object1"""`` 
    docstrings just on the next line after provider's definition.  It will 
    help code analyzing tools and IDE's to understand that variable above 
    contains some callable object, that returns particular instance as a 
    result of its call.

Here is an simple example of declarative catalog with several factories:

.. image:: /images/catalogs/declarative.png
    :width: 85%
    :align: center

.. literalinclude:: ../../examples/catalogs/declarative.py
   :language: python

:py:class:`dependency_injector.catalogs.DeclarativeCatalog` has several 
features that could be useful for some kind of operations on catalog's 
providers (please visit API docs for getting full list of feautes - 
:py:class:`dependency_injector.catalogs.DeclarativeCatalog`):

Example:

.. image:: /images/catalogs/declarative_api.png
    :width: 100%
    :align: center

.. literalinclude:: ../../examples/catalogs/declarative_api.py
   :language: python