Create custom events

Before creating your own custom chat events, learn how Chat SDK handles PubNub and chat-specific events.

Event handling

PubNub events

If you were to use a standard PubNub SDK, such as the Kotlin SDK, to build a chat app, you would have to perform additional steps as part of your PubNub initialization:

Explicitly subscribe to the chosen channel(s) to receive messages.
Add event listeners for your app to receive and handle all messages, signals, and events sent to the channel(s) you are subscribed to.

Luckily, the Chat SDK does this work automatically for you as part of other methods you will run on various entities to build and work with your chat app.

All these methods also return a function you can invoke to stop receiving events of a given type and unsubscribe from the channel. Follow the links to method descriptions for details and examples.

Entity	Method	Events handled
`Channel`	`streamUpdates()` or `streamUpdatesOn()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `objects` events of type `channel`.
`User`	`streamUpdates()` or `streamUpdatesOn()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `objects` events of type `uuid`.
`Message`	`streamUpdates()` or `streamUpdatesOn()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `messageAction` events (for message and message reactions changes) of type `added` or `removed`.
`Membership`	`streamUpdates()` or `streamUpdatesOn()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `objects` events of type `membership`.
`Channel`	`connect()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `message` events of type `text`.
`Channel`	`getTyping()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `signal` events of type `typing`.
`Channel`	`streamPresence()`	(Un)Subscribe the current user to/from a channel and start/stop getting all `presence` events of type `action` (responsible for monitoring when users join, leave the channels, or when their channel connection times out and they get disconnected).

Chat SDK wraps all events returned as HTTP responses from the server into meaningful and handy entities, like Channel, Message, User. These objects contain methods you can invoke to build your chat app and parameters you can display on your app's UI.

Chat events

Events, just like messages, are separate entities in the Chat SDK that carry data as a payload. Contrary to messages, however, events are not merely data transmitters but can trigger additional business logic. For example, in the Chat SDK, the Typing Indicator feature relies on events - based on whether a user is typing or not, the typing indicator starts or stops.

Chat SDK handles a few intrinsic types of such events that get emitted automatically when a user:

Reports a message (report event type)
Starts/Stops typing a message on a channel (typing event type)
Mentions someone else in the message (mention event type)
Reads a message published on a channel (receipt event type)
Invites another user to join a channel (invite event type)
Mutes a user, bans them, or removes these restrictions (moderation event type)

All event types use underneath the PubNub Pub/Sub API and one of these methods:

publish() - if event history is required, like for storing reported messages. For the purpose of the Chat SDK, history is always enabled when emitting an event with the publish() method.
signal() - if no event history is required, like in the case of the typing indicator that relies on short-lived signals.

Different Chat SDK methods emit (handle) different chat event types. For example, the sendText() method called on the Channel object emits mention events because the IDs of the mentioned users are always passed as part of published messages.

To listen to those events, Chat SDK uses two methods:

listenForEvents() for the current events that are emitted with the signal() or publish() method.
getEventsHistory() to get historical events that were emitted with the publish() method.

Events history limitations

The getEventsHistory() method uses PubNub Message Persistence API which has limitations - you cannot filter the results by type. Calling this method would return all event types that happened on a given channel in a given timeframe as long as they were emitted with the publish() method that stores history. Check custom events for an example showing this method.

The payload structure of the chat events is fixed and depends on the event type.

Read the subsections to get a better overview of each event type - check how they work and get some ideas on using them in your chat app to trigger additional business logic.

Events for reported messages

Type: report
PubNub method: PubNub method used to send events you listen for. publish() (with history) is used for all events related to message reporting.
Target: PUBNUB_INTERNAL_MODERATION_{channel_id}
Trigger: report() method on the Message object
Listener: streamMessageReports() (current) and getMessageReportsHistory (historical)
Sample use case: Message moderation. You might want to create a UI for an operational dashboard to monitor and manage all reported messages.
Payload:

@SerialName("report")
    class Report(
        // content of the flagged message
        val text: String? = null,
        // reason for flagging the message
        val reason: String,
        // timetoken of the flagged message
        val reportedMessageTimetoken: Long? = null,
        // channel where message was flagged
        val reportedMessageChannelId: String? = null,
        // author of the flagged message
        val reportedUserId: String?,
    ) : EventContent()

Events for typing indicator

Type: typing
PubNub method: PubNub method used to send events you listen for. signal() (without history) is used for all events related to typing.
Target: The same channel where messages are published.
Trigger: startTyping() and stopTyping() methods on the Channel object
Listener: getTyping() on the Channel object
Sample use case: Typing indicator. You might want to show graphically on the channel that another channel member is typing or has stopped typing a message.
Payload:

@SerialName("typing")
    class Typing(
        // value showing whether someone is typing or not
        val value: Boolean
    ) : EventContent()

Events for mentions

Type: mention
PubNub method: PubNub method used to send events you listen for. publish() (with history) is used for all events related to mentions.
Target: Unlike in other event types, a target for mention events is equal to a user ID. This ID is treated as a user-specific channel and is used to send system notifications about changes concerning a User object, such as creating, updating, or deleting that user. The channel name is equal to the ID (id) of the user and you can retrieve it by calling the currentUser method on the Chat object.
Trigger: sendText() method on the Channel object
Listener: listenForEvents() (current) or getEventsHistory() (historical) on the Chat object
Sample use case: User mentions. You might want to receive notifications for all events emitted when you are mentioned in a parent or thread channel.
Payload:

@SerialName("mention")
    class Mention(
        // timetoken of the message where someone is mentioned
        val messageTimetoken: Long,
        // channel on which the message with mention was sent
        val channel: String,
        // parent channel on which the message with mention was sent
        val parentChannel: String? = null
    ) : EventContent()

Events for read receipts

Type: receipt
PubNub method: PubNub method used to send events you listen for. signal() (with history persisted as the last read message on the Membership object) is used for all events related to message read receipts.
Target: The same channel where messages are published.
Trigger: markAllMessagesAsRead() method on the Chat object, the setLastReadMessageTimetoken() method on the Membership object, and the setLastReadMessage() method on the Membership object
Listener: streamReadReceipts() (current) on the Chat object
Sample use case: Read receipts. You might want to indicate on a channel - through avatars or some other indicator - that a message was read by another user/other users.
Payload:

@SerialName("receipt")
    class Receipt(
        // timetoken of the read message
        val messageTimetoken: Long
    ) : EventContent()

Events for channel initations

Type: invite
PubNub method: PubNub method used to send events you listen for. publish() (with history) is used for all events related to channel invitations.
Target: An event is sent to the ID of the invited user (user channel with the name same as the user ID).
Trigger: invite() and inviteMultiple methods on the Channel object
Listener: listenForEvents() (current) or getEventsHistory() (historical) on the Chat object
Sample use case: Channel invitations. You might want to notify users that they were invited to join a channel.
Payload:

@SerialName("invite")
    class Invite(
        // type of a channel to which a user was invited (direct or group)
        val channelType: ChannelType,
        // ID of the channel to which a user was invited
        val channelId: String
    ) : EventContent()

Events for user moderation

Type: moderation
PubNub method: PubNub method used to send events you listen for. publish() (with history) is used for all events related to user restrictions.
Target: An event is sent to the ID of the moderated user (user channel with the name same as the user ID).
Trigger: setRestrictions() methods on the Channel, Chat, and User objects
Listener: listenForEvents() (current) or getEventsHistory() (historical) on the Chat object
Sample use case: User moderation. You might want to notify users when they were muted, banned, or when you remove these restrictions from them.
Payload:

@SerialName("moderation")
    class Moderation(
        // ID of the channel on which the user's moderation restrictions were set or lifted
        val channelId: String,
        // type of restriction: whether a user was muted, banned, or at least one of these restrictions was removed ("lifted")
        val restriction: RestrictionType,
        // reason for muting or banning the user
        val reason: String? = null
    ) : EventContent()

Custom events

Chat SDK provides an additional type of events called custom. As the type name suggests, they are meant to let you carry your custom payloads and use them to perform additional business logic in your chat app.

With Chat SDK, you can:

Trigger such custom events using the emitEvent() method.
Listen to them with the listenForEvents() method.
Get all historical events using the getEventsHistory() method.

Create and send events

emitEvent() handles (constructs and sends) events with your custom payload.

In its logic, you can compare this method to the sendText() method used for sending new messages.

Method signature

This method takes the following parameters:

fun <T : EventContent> emitEvent(
        channelId: String,
        payload: T,
        mergePayloadWith: Map<String, Any>? = null,
    ): PNFuture<PNPublishResult>

Input

Parameter	Type	Required	Default	Description
`channelId`	`String`	Yes (all non-`mention` events)	n/a	Channel where you want to send the events.
`payload`	`T`	Yes	n/a	The payload of the emitted event. Use one of [EventContent] subclasses, for example: [EventContent.Mention], [EventContent.TextMessageContent] or [EventContent.Custom] for sending arbitrary data.
`mergePayloadWith`	`Map<String, Any>`	Yes	n/a	Metadata in the form of key-value pairs you want to pass as events from your chat app. Can contain anything in case of `custom` events, but has a predefined structure for other types of events.

Output

Type	Description
`PNFuture<PNPublishResult>`	Result of the PubNub Publish or Signal call.

Basic usage

You want to monitor a high-priority channel with a keyword spotter that identifies dissatisfaction words like "annoyed," "frustrated," or "angry." Suppose a message sent by any of the customers present on this channel contains any of these words. In that case, you want to resend it (with relevant metadata) to a separate technical channel (CUSTOMER-SATISFACTION-CREW) that's monitored by the team responsible for customer satisfaction.

val channelId = "CUSTOMER-SATISFACTION-CREW"
val customPayloads = EventContent.Custom(
    data = mapOf(
        "chatID" to "chat1234",
        "timestamp" to "2022-04-30T10:30:00Z",
        "customerID" to "customer5678",
        "triggerWord" to "frustrated"
    )
)

chat.emitEvent(channelId = channelId, payload = customPayloads).async { result ->
    result.onSuccess { pnPublishResult: PNPublishResult ->
        println("Message successfully emitted having timetoken: ${pnPublishResult.timetoken}")
    }.onFailure { ex: PubNubException ->
        println("Failed to emitEvent.")
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Receive current events

listenForEvents() lets you watch a selected channel for any new custom events emitted by your chat app. You can decide what to do with the incoming custom events and handle them using the callback function.

In its logic, you can compare this method to the connect() method used for receiving new messages.

Method signature

This method takes the following parameters:

fun <reified T : EventContent> Chat.listenForEvents(
    channelId: String,
    customMethod: EmitEventMethod = EmitEventMethod.PUBLISH,
    noinline callback: (event: Event<T>) -> Unit
): AutoCloseable

Input

Parameter	Type	Required	Default	Description
`T`	`reified T : EventContent`	Yes	n/a	Reified type parameter bounded by the `EventContent` interface, allowing access to type information at runtime.
`channelId`	`String`	Yes	n/a	Channel to listen for new events.
`customMethod`	`String`	No	n/a	An optional method used for emitting events. Used when listening to `Custom` events. If not provided, defaults to `PUBLISH`.
`callback`	`noinline (event: Event<T>) -> Unit`	Yes	n/a	A lambda function that is called with an `Event<T>` as its parameter. It defines the custom behavior to be executed whenever an event is detected on the specified channel.

Output

Type	Description
`AutoCloseable`	Interface that lets you stop receiving updates by invoking the `close()` method.

Basic usage

Monitor a channel for frustrated customer events. When such an event occurs, the handleFrustratedEvent function responds with a message acknowledging the customer's frustration and offering assistance.

// simulated event data received
val eventData = mapOf(
    "chatID" to "chat1234",
    "timestamp" to "2022-04-30T10:30:00Z",
    "customerID" to "customer5678",
    "triggerWord" to "frustrated"
);

// example function to handle the "frustrated" event and satisfy the customer
fun handleFrustratedEvent(eventData: EventContent.Custom) {
    // extract relevant information from the event data
    val customerID = eventData.data["customerID"]
    val timestamp = eventData.data["timestamp"]
    val triggerWord = eventData.data["triggerWord"]

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Get historical events

getEventsHistory() lets you get historical events from a selected channel.

In its logic, you can compare this method to the getHistory() method used for receiving historical messages. Similarly to this method, you cannot filter the results by type, so you'll get all events emitted with the publish() method that happened on a given channel in a given timeframe (not only custom events).

Method signature

This method takes the following parameters:

chat.getEventsHistory(
    channelId: String,
    startTimetoken: Long? = null,
    endTimetoken: Long? = null,
    count: Int?
    
): PNFuture<GetEventsHistoryResult>

Input

Parameter	Type	Required	Default	Description
`channelId`	`String`	Yes	n/a	Channel from which you want to pull historical messages.
`startTimetoken`	`Long`	No	n/a	Timetoken delimiting the start of a time slice (exclusive) to pull events from. For details, refer to the History section.
`endTimetoken`	`Long`	No	n/a	Timetoken delimiting the end of a time slice (inclusive) to pull events from. For details, refer to the History section.
`count`	`Int`	No	`100`	Number of historical events to return for the channel in a single call. You can pull a maximum number of 100 events in a single call.

Output

Parameter	Type	Description
`PNFuture<GetEventsHistoryResult>`	`object`	Returned object containing two fields: `events` and `isMore`.
→ `events`	`Set<Event<EventContent>>`	Array listing the requested number of historical events objects.
→ `isMore`	`Boolean`	Info whether there are more historical events to pull.

Basic usage

Fetch the last 10 historical events from the CUSTOMER-SATISFACTION-CREW channel.

chat.getEventsHistory(
        channelId = "CUSTOMER-SATISFACTION-CREW",
        count = 10
).async { result -> 
    // ... 
}

Event handling​

PubNub events​

Chat events​

Events history limitations

Events for reported messages​

Events for typing indicator​

Events for mentions​

Events for read receipts​

Events for channel initations​

Events for user moderation​

Custom events​

Create and send events​

Method signature​

Input​

Output​

Basic usage​

Receive current events​

Method signature​

Input​

Output​

Basic usage​

Get historical events​

Method signature​

Input​

Output​

Basic usage​

Event handling

PubNub events

Chat events

Events for reported messages

Events for typing indicator

Events for mentions

Events for read receipts

Events for channel initations

Events for user moderation

Custom events

Create and send events

Method signature

Input

Output

Basic usage

Receive current events

Method signature

Input

Output

Basic usage

Get historical events

Method signature

Input

Output

Basic usage