Publish/Subscribe API for Swift Native SDK

PubNub delivers messages worldwide in less than 30 ms. Send a message to one recipient or broadcast to thousands of subscribers.

For higher-level conceptual details on publishing and subscribing, refer to Connection Management and to Publish Messages.

Publish​

publish() sends a message to all channel subscribers. PubNub replicates the message across its points of presence and delivers it to all subscribed clients on that channel. All publish calls are performed asynchronously.

  • You must initialize PubNub with the publishKey.
  • You don't have to be subscribed to a channel to publish to it.
  • You cannot publish to multiple channels simultaneously.

Method(s)​

To Publish a message you can use the following method(s) in the Swift SDK:

func publish(
    channel: String,
    message: JSONCodable,
    customMessageType: String? = nil,
    shouldStore: Bool? = nil,
    storeTTL: Int? = nil,
    meta: AnyJSON? = nil,
    shouldCompress: Bool = false,
    custom requestConfig: PubNub.RequestConfiguration = PubNub.RequestConfiguration(),
    completion: ((Result<Timetoken, Error>) -> Void)?
)
* required
ParameterDescription
channel *
Type: String
Default:
n/a
The channel ID to publish to.
message *
Type: JSONCodable
Default:
n/a
The message to publish.
customMessageType
Type: String?
Default:
nil
A case-sensitive, alphanumeric string from 3 to 50 characters describing the business-specific label or category of the message. Dashes - and underscores _ are allowed. The value cannot start with special characters or the string pn_ or pn-.

Examples: text, action, poll.
shouldStore
Type: Bool?
Default:
nil
If true the published message is stored in history.
storeTTL
Type: Int?
Default:
nil
Set a per message time to live in Message Persistence. 1. If shouldStore = true, and storeTTL = 0, the message is stored with no expiry time. 2. If shouldStore = true and storeTTL = X (X is an Integer value), the message is stored with an expiry time of X hours. 3. If shouldStore is false or not specified, the message isn't stored and the storeTTL parameter is ignored. 4. If storeTTL isn't specified, then expiration of the message defaults back to the expiry value for the key.
meta
Type: JSONCodable?
Default:
nil
Publish extra meta with the request.
shouldCompress
Type: Bool
Default:
false
When true, the SDK uses HTTP POST to publish the messages. The message is sent in the BODY of the request, instead of the query string when HTTP GET is used. Also the messages are compressed thus reducing the size of the messages.
custom
Default:
PubNub.RequestConfiguration()
An object that allows for per-request customization of PubNub configuration or network session. For more information, refer to the Request configuration section.
completion
Type: ((Result<Timetoken, Error>) -> Void)?
Default:
nil
The async Result of the method call.

Completion handler result​

Success​

The Timetoken of the published Message.

Failure​

An Error describing the failure.

Sample code​

Publish a message to a channel​

Reference code
This example is a self-contained code snippet ready to be run. It includes necessary imports and executes methods with console logging. Use it as a reference when working with other examples in this document.

Subscribe to the channel

Before running the above publish example, either using the Debug Console or in a separate script running in a separate terminal window, subscribe to the same channel that is being published to.

Other examples​

Publish a dictionary object​


Publish the above dictionary as a custom Swift Object​


Mix and match types with custom objects​


Publish an APNs2 push notification​


Root level push message object​

public struct PubNubPushMessage: JSONCodable {
  
  /// The payload delivered via Apple Push Notification service (APNS)
  public let apns: PubNubAPNSPayload?

  /// The payload delivered via Firebase Cloud Messaging service (FCM)
  public let fcm: PubNubFCMPayload?

  /// Additional message payload sent outside of the push notification
  ///
  /// In order to guarantee valid JSON any scalar values will be assigned to the `data` key.
  /// Non-scalar values will retain their coding keys.
  public var additionalMessage: JSONCodable?
}

Fire​

The fire endpoint sends a message to Functions event handlers and Illuminate. The message goes directly to handlers registered on the target channel and triggers their execution. The handler can read the request body. Messages sent via fire() aren't replicated to subscribers and aren't stored in history.

Method(s)​

To Fire a message you can use the following method(s) in the Swift SDK:

func fire(
    channel: String,
    message: JSONCodable,
    meta: JSONCodable? = nil,
    custom requestConfig: PubNub.RequestConfiguration = PubNub.RequestConfiguration(),
    completion: ((Result<Timetoken, Error>) -> Void)?
)
* required
ParameterDescription
channel *
Type: String
Default:
n/a
The channel ID to fire to.
message *
Type: JSONCodable
Default:
n/a
The message to fire.
meta
Type: JSONCodable?
Default:
nil
Publish extra meta with the request.
custom
Default:
PubNub.RequestConfiguration()
An object that allows for per-request customization of PubNub configuration or network session. For more information, refer to the Request configuration section.
completion
Type: ((Result<Timetoken, Error>) -> Void)?
Default:
nil
The async Result of the method call.

Completion handler result​

Success​

The Timetoken of the published Message.

Failure​

An Error describing the failure.

Sample code​

Fire a message to a channel​


Signal​

The signal() function sends a signal to all subscribers of a channel.

By default, signals are limited to a message payload size of 64 bytes. This limit applies only to the payload, and not to the URI or headers. If you require a larger payload size, please contact support.

Method(s)​

To Signal a message you can use the following method(s) in the Swift SDK:

func signal( 
  channel: String, 
  message: JSONCodable,
  customMessageType: String? = nil,
  custom requestConfig: PubNub.RequestConfiguration = PubNub.RequestConfiguration(),
  completion: ((Result<Timetoken, Error>) -> Void)?
)
* required
ParameterDescription
channel *
Type: String
Default:
n/a
The channel ID to send a signal to.
message *
Type: JSONCodable
Default:
n/a
The message to signal.
customMessageType
Type: String?
Default:
nil
A case-sensitive, alphanumeric string from 3 to 50 characters describing the business-specific label or category of the message. Dashes - and underscores _ are allowed. The value cannot start with special characters or the string pn_ or pn-.

Examples: text, action, poll.
custom
Default:
PubNub.RequestConfiguration()
An object that allows for per-request customization of PubNub configuration or network session. For more information, refer to the Request configuration section.
completion
Type: ((Result<Timetoken, Error>) -> Void)?
Default:
nil
The async Result of the method call.

Completion handler result​

Success​

The Timetoken of the published Message.

Failure​

An Error describing the failure.

Sample code​

Signal a message to a channel​


Subscribe​

Subscribe opens a TCP socket and listens for messages and events on a specified entity or set of entities. Set subscribeKey during initialization.

Conceptual overview

For more general information about subscriptions, refer to Subscriptions.

Entities are first-class citizens that expose their APIs. You can subscribe using the PubNub client or directly on a specific entity:

After subscribe(), the client receives new messages. Configure automaticRetry to reconnect and fetch available messages after a disconnect.

Subscription scope​

Subscriptions let you attach listeners for specific real-time update types. Your app receives messages and events through those listeners. There are two types:

  • Subscription: created from an entity and scoped to that entity (for example, a particular channel)
  • SubscriptionSet: created from the PubNub client and scoped to the client (for example, all subscriptions created on a single pubnub object). A set can include one or more subscriptions.

One event listener receives all messages, signals, and events for the entities you subscribe to. To add listeners, see Event listeners.

Create a subscription​

An entity-level Subscription allows you to receive messages and events for only that entity for which it was created. Using multiple entity-level Subscriptions is useful for handling various message/event types differently in each channel.

Keep a strong reference

You should keep a strong reference to every created subscription/subscription set because they must stay in memory to listen for updates. If you were to create a Subscription/SubscriptionSet and not keep a strong reference to it, Automatic Reference Counting (ARC) could deallocate the Subscription as soon as your code finishes executing.

To create a subscription object, call the following method on any entity defined in the Entities section:

// Entity-based, local-scoped
func subscription(
  queue: DispatchQueue = .main,
  options: SubscriptionOptions = SubscriptionOptions.empty()
)
* required
ParameterDescription
options
Type: SubscriptionOptions
Subscription behavior configuration.

Create a subscription set​

A client-level SubscriptionSet allows you to receive messages and events for all entities. A single SubscriptionSet is useful for similarly handling various message/event types in each channel.

Keep a strong reference

You should keep a strong reference to every created subscription/subscription set because they must stay in memory to listen for updates. If you were to create a Subscription/SubscriptionSet and not keep a strong reference to it, Automatic Reference Counting (ARC) could deallocate the Subscription as soon as your code finishes executing.

To create a SubscriptionSet, call the following method on a PubNub instance:

// Client-based, general-scoped
func subscription(
    queue: DispatchQueue = .main,
    entities: any Collection<Subscribable>,
    options: SubscriptionOptions = SubscriptionOptions.empty()
) -> SubscriptionSet
* required
ParameterDescription
queue
Type: DispatchQueue
An underlying queue to dispatch events. Defaults to the main queue.
entities *
Type: Collection<Subscribable>
One or more entities to create a subscription of. Available values include: ChannelRepresentation, ChannelGroupRepresentation, UserMetadataRepresentation, ChannelMetadataRepresentation.
options
Type: SubscriptionOptions
Subscription behavior configuration.
Add/remove sets

You can add and remove subscriptions to create new sets. Refer to the Other examples section for more information.

SubscriptionOptions​

SubscriptionOptions is the base class for all possible options. Available subclasses are:

OptionDescription
ReceivePresenceEvents
Whether presence updates for userIds should be delivered through the listener streams.

For information on how to receive presence events and what those events are, refer to Presence Events.

Method(s)​

Subscription and SubscriptionSet use the same subscribe() method.

Subscribe​

To subscribe, you can use the following method in the Swift SDK:

func subscribe(with: Timetoken? = nil)
* required
ParameterDescription
with
Type: Timetoken
Timetoken from which to return any available cached messages. Message retrieval with timetoken is not guaranteed and should only be considered a best-effort service.

If the value is not a 17-digit number, the provided value will be ignored.
Sample code​

Other examples​
Create a subscription set from 2 individual subscriptions​

Returns​

The subscribe() method doesn't have a return value.

Entities​

Entities are subscribable objects for which you can receive real-time updates (messages, events, etc).

The following methods can be called on a PubNub instance to create a local entity:

Create channels​

This method returns a local ChannelRepresentation entity.

func channel(_ name: String) -> ChannelRepresentation
* required
ParameterDescription
channel *
Type: String
The ID of the channel to create a subscription of.

Sample code​


Create a channel group​

This method returns a local ChannelGroupRepresentation entity.

func channelGroup(_ name: String) -> ChannelGroupRepresentation
* required
ParameterDescription
name *
Type: String
The name of the channel group to create a subscription of.

Sample code​


Create channel metadata​

This method returns a local ChannelMetadataRepresentation entity.

func channelMetadata(_ name: String) -> ChannelMetadataRepresentation
* required
ParameterDescription
name *
Type: String
The String identifier of the channel metadata object to create a subscription of.

Sample code​


Create user metadata​

This method returns a local UserMetadataRepresentation entity.

func userMetadata(_ name: String) -> UserMetadataRepresentation
* required
ParameterDescription
name *
Type: String
The String identifier of the user metadata object to create a subscription of.

Sample code​


Event listeners​

Messages and events are received in your app using a listener. This listener allows a single point to receive all messages, signals, and events.

You can attach listeners to the instances of Subscription, SubscriptionSet, and, in the case of the connection status, the PubNub client.

Add listeners​

You can implement multiple listeners with the onEvent closure or register an event-specific listener that receives only a selected type, like message or file.

Method(s)​









Add connection status listener​

The PubNub client has a listener dedicated to handling connection status updates.

Client scope

This listener is only available on the PubNub object.

Method(s)​

var onConnectionStateChange: ((ConnectionStatus) -> Void)?

Sample code​


Returns​

The subscription status. For information about available statuses, refer to SDK statuses.

Clone​

Create a clone of an existing subscription with the same subscription state but an empty closures of real-time event listeners.

Method(s)​

// Method in the `Subscription` class
func clone() -> Subscription
// Method in the `SubscriptionSet` class
func clone() -> SubscriptionSet

Sample code​


Returns​

A new instance of the subscription object with an empty event dispatcher.

Unsubscribe​

Stop receiving real-time updates from a Subscription or a SubscriptionSet.

Method(s)​

func unsubscribe()

Sample code​


Returns​

None

Unsubscribe all​

Remove the client's active subscriptions from all channels. It clears out the list of channels the client is currently listening to.

Client scope

This method is only available on the PubNub object.

Method(s)​

func unsubscribeAll()

Sample code​


Returns​

None

Subscribe (old)​

Not recommended

The use of this method is discouraged. Use Subscribe instead.

Receive messages​

Your app receives messages and events via event listeners. The event listener is a single point through which your app receives all the messages, signals, and events that are sent in any channel you are subscribed to.

For more information about adding a listener, refer to the Event Listeners section.

Description​

This function causes the client to create an open TCP socket to the PubNub Real-Time Network and begin listening for messages on a specified channel ID. To subscribe to a channel ID the client must send the appropriate subscribeKey at initialization.

By default a newly subscribed client will only receive messages published to the channel after the subscribe() call completes.

The PubNub Swift SDK removes (dedupes) messages automatically if they have the same timetoken, publisher, and payload.

Unsubscribing from all channels

Unsubscribing from all channels, and then subscribing to a new channel Y is not the same as subscribing to channel Y and then unsubscribing from the previously-subscribed channel(s). Unsubscribing from all channels resets the last-received timetoken and thus, there could be some gaps in the subscription that may lead to message loss.

Method(s)​

To Subscribe to a channel you can use the following method(s) in the Swift SDK:

func subscribe(
    to channels: [String],
    and channelGroups: [String] = [],
    at timetoken: Timetoken? = nil,
    withPresence: Bool = false
)
* required
ParameterDescription
to *
Type: [String]
Default:
n/a
An array of channels to subscribe to.
and
Type: [String]
Default:
[]
An array of channel groups to subscribe to.
at
Type: Timetoken?
Default:
nil
The timetoken integer to start the subscription from.
withPresence
Type: Bool
Default:
false
If true it also subscribes to presence events on the specified channels.
filterOverride
Type: String?
Default:
nil
Overrides the previous filter on the next successful request

Sample code​

Subscribe to a channel:


Event listeners

The response of the call is handled by adding a Listener. Please see the Listeners section for more details. Listeners should be added before calling the method.

Other examples​

Subscribing to multiple channels​

It's possible to subscribe to more than one channel using the Multiplexing feature. The example shows how to do that using an array to specify the channel names.

Alternative subscription methods

You can also use Wildcard Subscribe and Channel Groups to subscribe to multiple channels at a time. To use these features, the Stream Controller add-on must be enabled on your keyset in the Admin Portal.


Subscribing to a Presence channel​
Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

For any given channel there is an associated Presence channel. You can subscribe directly to the channel by appending -pnpres to the channel name. For example the channel named my_channel would have the presence channel named my_channel-pnpres.


Wildcard subscribe to channels​
Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal (with Enable Wildcard Subscribe checked). Read the support page on enabling add-on features on your keys.

Wildcard subscribes allow the client to subscribe to multiple channels using wildcard. For example, if you subscribe to a.* you will get all messages for a.b, a.c, a.x. The wildcarded * portion refers to any portion of the channel string name after the dot (.).


Wildcard grants and revokes

Only one level (a.*) of wildcarding is supported. If you grant on * or a.b.*, the grant will treat * or a.b.* as a single channel named either * or a.b.*. You can also revoke permissions from multiple channels using wildcards but only if you previously granted permissions using the same wildcards. Wildcard revokes, similarly to grants, only work one level deep, like a.*.

Subscribe to a channel group​
Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.


Subscribe to the Presence channel of a channel group​
Requires Stream Controller and Presence add-ons

This method requires both the Stream Controller and Presence add-ons are enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.


Subscribing to multiple channel groups​
Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.


Subscribing to a channel and channel group simultaneously​
Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.


Event listeners​

You can be notified of connectivity status, message, and presence notifications via the listeners.

Listeners should be added before calling the method.

Add listeners​

How to check UUID

You can check the UUID of the publisher of a particular message by checking the message.publisher property in the subscription listener.

Remove listeners​

The SubscriptionListener can be removed by either calling listener.cancel(), or by letting it fall out of scope and be removed as an autoreleased object.

Listener subscription Events​

This is the list of SubscriptionEvent case types that can be emitted from didReceiveSubscription, or grouped together using didReceiveBatchSubscription. Each event case also has a standalone listener that can save code space, but will be functionally equivalent to using didReceiveSubscription.

CaseTypeStandalone ListenerDescription
messageReceived
PubNubMessage
didReceiveMessage
Messages sent to subscribed channels/groups
signalReceived
PubNubMessage
didReceiveSignal
Signals sent to subscribed channels/groups
connectionStatusChanged
ConnectionStatus
didReceiveStatus
Changes in the connection to the PubNub system
subscriptionChanged
SubscriptionChangeEvent
didReceiveSubscriptionChange
Notifies when channels/groups are subscribed or unsubscribed
presenceChanged
PubNubPresenceChange
didReceivePresence
Presence changes on subscribed channels/groups tracking presence
uuidMetadataSet
PubNubUUIDMetadataChangeset
didReceiveObjectMetadataEvent
UUID metadata was set
uuidMetadataRemoved
String
didReceiveObjectMetadataEvent
UUID metadata was removed
channelMetadataSet
PubNubChannelMetadataChangeset
didReceiveObjectMetadataEvent
Channel metadata was set
channelMetadataRemoved
String
didReceiveObjectMetadataEvent
Channel metadata was removed
membershipMetadataSet
PubNubMembershipMetadata
didReceiveObjectMetadataEvent
Membership metadata was set
membershipMetadataRemoved
PubNubMembershipMetadata
didReceiveObjectMetadataEvent
Membership metadata was removed
messageActionAdded
PubNubMessageAction
didReceiveMessageAction
A PubNubMessageAction was added to a published message
messageActionRemoved
PubNubMessageAction
didReceiveMessageAction
A PubNubMessageAction was removed from a published message
subscribeError
PubNubError
subscribeError
Any error that might have occurred during the subscription stream

Sample code​

This is an example using didReceiveBatchSubscription to allow you to receive multiple events per event call.


Other examples​

For didReceiveSubscription, simply rename the remove the for...in loop while keeping the event switch:


Unsubscribe (old)​

Not recommended

The use of this method is discouraged. Use Unsubscribe instead.

When subscribed to a single channel, this function causes the client to issue a leave from the channel and close any open socket to the PubNub Network. For multiplexed channels, the specified channel(s) will be removed and the socket remains open until there are no more channels remaining in the list.

Unsubscribing from all channels

Unsubscribing from all channels, and then subscribing to a new channel Y is not the same as subscribing to channel Y and then unsubscribing from the previously-subscribed channel(s). Unsubscribing from all channels resets the last-received timetoken and thus, there could be some gaps in the subscription that may lead to message loss.

Method(s)​

To Unsubscribe from a channel you can use the following method(s) in the Swift SDK:

func unsubscribe(from channels: [String], and channelGroups: [String] = [])
* required
ParameterDescription
from *
Type: Array
Default:
n/a
The list of channels to unsubscribe from.
and
Type: Array
Default:
[]
The list of channel groups to unsubscribe from.
presenceOnly
Type: Bool
Default:
false
If true it only unsubscribes from presence events on the specified channels.

Sample code​

Unsubscribe from a channel:


Other examples​

Unsubscribing from multiple channels​
Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.


Unsubscribing from multiple channel groups​
Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.


Unsubscribe all (old)​

Deprecated

This method is deprecated. Use Unubscribe all instead.

Unsubscribe from all channels and all channel groups

Method(s)​

func unsubscribeAll()

Sample code​


Returns​

None

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