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72 lines
2.2 KiB
ReStructuredText
72 lines
2.2 KiB
ReStructuredText
####################
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Dependency injection
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####################
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Dependency injection is a programming technique that makes a class independent of its dependencies.
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It achieves that by decoupling the usage of an object from its creation.
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This helps you to follow `SOLID's <https://en.wikipedia.org/wiki/SOLID>`_ dependency
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inversion and single responsibility principles.
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How it works in aiogram
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=======================
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For each update :class:`aiogram.dispatcher.dispatcher.Dispatcher` passes handling context data.
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Filters and middleware can also make changes to the context.
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To access contextual data you should specify corresponding keyword parameter in handler or filter.
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For example, to get :class:`aiogram.fsm.context.FSMContext` we do it like that:
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.. code-block:: python
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@router.message(ProfileCompletion.add_photo, F.photo)
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async def add_photo(
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message: types.Message, bot: Bot, state: FSMContext
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) -> Any:
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... # do something with photo
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Injecting own dependencies
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==========================
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Aiogram provides several ways to complement / modify contextual data.
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The first and easiest way is to simply specify the named arguments in
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:class:`aiogram.dispatcher.dispatcher.Dispatcher` initialization, polling start methods
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or :class:`aiogram.webhook.aiohttp_server.SimpleRequestHandler` initialization if you use webhooks.
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.. code-block:: python
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async def main() -> None:
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dp = Dispatcher(..., foo=42)
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return await dp.start_polling(
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bot, bar="Bazz"
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)
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Analogy for webhook:
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.. code-block:: python
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async def main() -> None:
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dp = Dispatcher(..., foo=42)
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handler = SimpleRequestHandler(dispatcher=dp, bot=bot, bar="Bazz")
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... # starting webhook
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:class:`aiogram.dispatcher.dispatcher.Dispatcher`'s workflow data also can be supplemented
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by setting values as in a dictionary:
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.. code-block:: python
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dp = Dispatcher(...)
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dp["eggs"] = Spam()
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The middlewares updates the context quite often.
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You can read more about them on this page:
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- :ref:`Middlewares <middlewares>`
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The last way is to return a dictionary from the filter:
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.. literalinclude:: ../../examples/context_addition_from_filter.py
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...or using :ref:`MagicFilter <magic-filters>` with :code:`.as_(...)` method.
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