112 lines
4.1 KiB
ReStructuredText
112 lines
4.1 KiB
ReStructuredText
Handling Updates
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================
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Calling `API methods`_ sequentially is cool, but how to react when, for example, a new message arrives? This page deals
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with updates and how to handle such events in Pyrogram. Let's have a look at how they work.
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Defining Updates
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----------------
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First, let's define what are these updates. As hinted already, updates are simply events that happen in your Telegram
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account (incoming messages, new members join, button presses, etc...), which are meant to notify you about a new
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specific state that changed. These updates are handled by registering one or more callback functions in your app using
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`Handlers <../api/handlers>`_.
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Each handler deals with a specific event and once a matching update arrives from Telegram, your registered callback
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function will be called and its body executed.
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Registering an Handler
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----------------------
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To explain how handlers work let's have a look at the most used one, the
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:obj:`MessageHandler <pyrogram.MessageHandler>`, which will be in charge for handling :obj:`Message <pyrogram.Message>`
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updates coming from all around your chats. Every other handler shares the same setup logic; you should not have troubles
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settings them up once you learn from this section.
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Using add_handler()
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-------------------
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The :meth:`add_handler() <pyrogram.Client.add_handler>` method takes any handler instance that wraps around your defined
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callback function and registers it in your Client. Here's a full example that prints out the content of a message as
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soon as it arrives:
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.. code-block:: python
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from pyrogram import Client, MessageHandler
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def my_function(client, message):
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print(message)
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app = Client("my_account")
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my_handler = MessageHandler(my_function)
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app.add_handler(my_handler)
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app.run()
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Let's examine these four new pieces. First one: a callback function we defined which accepts two arguments -
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*(client, message)*. This will be the function that gets executed every time a new message arrives and Pyrogram will
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call that function by passing the client instance and the new message instance as argument.
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.. code-block:: python
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def my_function(client, message):
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print(message)
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Second one: the :obj:`MessageHandler <pyrogram.MessageHandler>`. This object tells Pyrogram the function we defined
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above must only handle updates that are in form of a :obj:`Message <pyrogram.Message>`:
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.. code-block:: python
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my_handler = MessageHandler(my_function)
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Third: the method :meth:`add_handler() <pyrogram.Client.add_handler>`. This method is used to actually register the
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handler and let Pyrogram know it needs to be taken into consideration when new updates arrive and the dispatching phase
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begins.
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.. code-block:: python
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app.add_handler(my_handler)
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Last one, the :meth:`run() <pyrogram.Client.run>` method. What this does is simply calling
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:meth:`start() <pyrogram.Client.start>` and a special method :meth:`idle() <pyrogram.Client.idle>` that keeps your main
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scripts alive until you press ``CTRL+C``; the client will be automatically stopped after that.
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.. code-block:: python
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app.run()
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Using Decorators
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----------------
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All of the above will become quite verbose, especially in case you have lots of handlers to register. A much nicer way
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to do so is by decorating your callback function with the :meth:`on_message() <pyrogram.Client.on_message>` decorator.
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.. code-block:: python
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from pyrogram import Client
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app = Client("my_account")
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@app.on_message()
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def my_handler(client, message):
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print(message)
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app.run()
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.. note::
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Due to how these decorators work in Pyrogram, they will wrap your defined callback function in a tuple consisting of
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``(handler, group)``; this will be the value held by your function identifier (e.g.: *my_function* from the example
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above).
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In case, for some reason, you want to get your own function back after it has been decorated, you need to access
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``my_function[0].callback``, that is, the *callback* field of the *handler* object which is the first element in the
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tuple, accessed by bracket notation *[0]*.
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.. _API methods: usage.html |