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Skygear Chat Cloud Function & Event Hooks


Skygear Chat event hooks are executed after any of the following actions are executed.

  • Message
    • Sending a message
    • Editing a message
    • Deleting a message
    • Typing a message
  • Conversation
    • Creating a conversation
    • Updating a conversation
    • Deleting a conversation
    • Adding participants to a conversation
    • Removing participants from a conversation

The below code snippet prints a message to server log after an user send a message.

from chat.hooks import *
from skygear.transmitter.encoding import deserialize_record
def after_message_sent_hook(message, conversation, participants):
    message = deserialize_record(message)
    conversation = deserialize_record(conversation)
    print('Message [%s] is sent to conversation [%s].' % (message['body'], conversation['title']))

Note: Currently only one of the same kind hooks can be registered.

Skygear Cloud Function

Please refer to Introduction to Cloud Functions for the basics of cloud function.

Available Event Hooks

Event hooks are implemented in Skygear Chat plugin project. Therefore, you need to import chat.hooks in order to use event hooks in cloud function.

The followings are the available event hooks.

  • after_message_sent: to run after a message is sent
  • after_message_updated: to run after a message is updated
  • after_message_deleted: to run after a message is deleted
  • typing_started: to run after typing is started
  • after_conversation_created: to run after a conversation is created
  • after_conversation_updated: to run after a conversation is update
  • after_conversation_deleted: to run after a conversation deleted
  • after_users_added_to_conversation: to run after one or more users are added to a conversation
  • after_users_removed_from_conversation: to run after one or more users are removed from the conversation

All decorated functions are not required to return any value.

Decorated Function Interfaces and Parameters

Depending on decorators, decorated functions contain any of the following parameters. All passing values are serialized values, therefore you need to call derserialize_record from skygear.encoding to retrieve corresponding Skygear record in python.

Tables Description
message Message Record
conversation Conversation Record
participants Array of User Record
events Array of Typing Events
new_users Array of User Records
old_users Array of User Records

Function Interfaces

Below are the list of function interfaces of each decorator.

def after_message_sent_hook(message, conversation, participants):
def after_message_updated_hook(message, conversation, participants):
def after_message_updated_deleted_hook(message, conversation, participants):
def typing_started_hook(conversation, participants, events):
def after_conversation_created_hook(conversation, participants):
def after_conversation_updated_hook(conversation, participants):
def after_conversation_deleted_hook(conversation, participants):
def after_users_added_to_conversation_hook(conversation, participants, new_users):
def after_users_removed_from_conversation_hook(conversation, participants, old_users):

Real Life Example: Push Notification

The following example demonstrates push notification implementation with Skygear API and Skygear Chat event hook. Function after_message_sent_hook is called after a message is sent. participants and message are then deserialized with deserialize_record. other_user_ids and notification are evaluated from participants and message respectively. Lastly, push_users is called and participants' devices receive notifications.

from skygear.transmitter.encoding import deserialize_record
from skygear.action import push_users
from skygear.container import SkygearContainer
from skygear.options import options as skyoptions
from skygear.utils.context import current_user_id
from chat.decorators import *

def after_message_sent_hook(message, conversation, participants):
    container = SkygearContainer(api_key=skyoptions.masterkey,
    message = deserialize_record(message)
    conversation = deserialize_record(conversation)
    other_user_ids = []
    current_user = None
    for record in participants:
        participant = deserialize_record(record)
        if == current_user_id():
            current_user = participant
    content = ''
    if 'body' in message:
        content = current_user['username'] + ": " + message['body']
        content = current_user['username'] + " sent you a file."
    notification = {'gcm': {
                       'notification': {
                           'title': conversation['title'],
                           'body': content
                    'apns': {
                        'aps': {
                            'alert': {
                                'title': conversation['title'],
                                'body': content
                            'from': 'skygear',
                            'operation': 'notification'
    push_users(container, other_user_ids, notification)

See Also

Demo project