PubNub 4.16.1 for iOS 9+

// Listener's class should conform to `PNEventsListener` protocol
// in order to have access to available callbacks.

// Adding listener.
[pubnub addListener:self];

// Callbacks listed below.

- (void)client:(PubNub *)pubnub didReceiveMessage:(PNMessageResult *)message {
    NSString *channel = message.data.channel; // Channel on which the message has been published
    NSString *subscription = message.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    NSNumber *timetoken = message.data.timetoken; // Publish timetoken
    id msg = message.data.message; // Message payload
    NSString *publisher = message.data.publisher; // Message publisher
}

- (void)client:(PubNub *)pubnub didReceiveSignal:(PNSignalResult *)signal {
    NSString *channel = message.data.channel; // Channel on which the signal has been published
    NSString *subscription = message.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    NSNumber *timetoken = message.data.timetoken; // Signal timetoken
    id msg = message.data.message; // Signal payload
    NSString *publisher = message.data.publisher; // Signal publisher
}

- (void)client:(PubNub *)pubnub didReceiveMessageAction:(PNMessageActionResult *)action {
    NSString *channel = action.data.channel; // Channel on which the message has been published
    NSString *subscription = action.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    NSString *event = action.data.event; // Can be: added or removed
    NSString *type = action.data.action.type; // Message action type
    NSString *value = action.data.action.value; // Message action value
    NSNumber *messageTimetoken = action.data.action.messageTimetoken; // Timetoken of the original message
    NSNumber *actionTimetoken = action.data.action.actionTimetoken; // Timetoken of the message action
    NSString *uuid = action.data.action.uuid; // UUID of user which added / removed message action
}

- (void)client:(PubNub *)pubnub didReceivePresenceEvent:(PNPresenceEventResult *)event {
    NSString *channel = message.data.channel; // Channel on which presence changes
    NSString *subscription = message.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    NSString *presenceEvent = event.data.presenceEvent; // Can be: join, leave, state-change, timeout or interval
    NSNumber *occupancy = event.data.presence.occupancy; // Number of users subscribed to the channel (not available for state-change event)
    NSNumber *timetoken = event.data.presence.timetoken; // Presence change timetoken
    NSString *uuid = event.data.presence.uuid; // UUID of user for which presence change happened

    // Only for 'state-change' event
    NSDictionary *state = event.data.presence.state; // User state (only for state-change event)

    // Only for 'interval' event
    NSArray<NSString *> *join = event.data.presence.join; // UUID of users which recently joined channel
    NSArray<NSString *> *leave = event.data.presence.leave; // UUID of users which recently leaved channel
    NSArray<NSString *> *timeout = event.data.presence.timeout; // UUID of users which recently timed out on channel
}

- (void)client:(PubNub *)pubnub didReceiveObjectEvent:(PNObjectEventResult *)event {
    NSString *channel = event.data.channel; // Channel to which the event belongs
    NSString *subscription = event.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    NSString *event = event.data.event; // Can be: set or delete
    NSString *type = event.data.type; // Entity type: channel, uuid or membership
    NSNumber *timestamp = event.data.timestamp; // Event timestamp

    PNChannelMetadata *channelMetadata = event.data.channelMetadata; // Updated channel metadata (only for channel entity type)
    PNUUIDMetadata *uuidMetadata = event.data.uuidMetadata; // Updated channel metadata (only for uuid entity type)
    PNMembership *membership = event.data.membership; // Updated channel metadata (only for membership entity type)
}

- (void)client:(PubNub *)pubnub didReceiveFileEvent:(PNFileEventResult *)event {
    NSString *channel = event.data.channel; // Channel to which file has been uploaded
    NSString *subscription = event.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    id message = event.data.message; // Message added for uploaded file
    NSString *publisher = event.data.publisher; // UUID of file uploader
    NSURL *fileDownloadURL = event.data.file.downloadURL; // URL which can be used to download file
    NSString *fileIdentifier = event.data.file.identifier; // Unique file identifier
    NSString *fileName = event.data.file.name; // Name with which file has been stored remotely
}

- (void)client:(PubNub *)pubnub didReceiveStatus:(PNStatus *)status {
    PNStatusCategory category = status.category; // One of PNStatusCategory fields to identify status of operation processing
    PNOperationType operation = status.operation; // One of PNOperationType fields to identify for which operation status received
    BOOL isError = status.isError; // Whether any kind of error happened.
    NSInteger statusCode = status.statusCode; // Related request processing status code
    BOOL isTLSEnabled = status.isTLSEnabled; // Whether secured connection enabled
    NSString *uuid = status.uuid; // UUID which configured for passed client
    NSString *authKey = status.authKey; // Auth key configured for passed client
    NSString *origin = status.origin; // Origin against which request has been sent
    NSURLRequest *clientRequest = status.clientRequest; // Request which has been used to send last request (may be nil)
    BOOL willAutomaticallyRetry = status.willAutomaticallyRetry; // Whether client will try to perform automatic retry

    // Following is available when operation == PNSubscribeOperation,
    // because status is PNSubscribeStatus instance in this case
    PNSubscribeStatus *subscribeStatus = (PNSubscribeStatus *)status;
    NSNumber *currentTimetoken = subscribeStatus.currentTimetoken; // Timetoken which has been used for current subscribe request
    NSNumber *lastTimeToken = subscribeStatus.lastTimeToken; // Timetoken which has been used for previous subscribe request
    NSArray<NSString *> *subscribedChannels = subscribeStatus.subscribedChannels; // List of channels on which client currently subscribed
    NSArray<NSString *> *subscribedChannelGroups = subscribeStatus.subscribedChannelGroups; // List of channel groups on which client currently subscribed
    NSString *channel = subscribeStatus.data.channel; // Name of channel to which status has been received
    NSString *subscription = subscribeStatus.data.subscription; // Wild-card channel or channel on which PubNub client actually subscribed
    NSNumber *timetoken = subscribeStatus.data.timetoken; // Timetoken at which event arrived
    NSDictionary *userMetadata = subscribeStatus.data.userMetadata; // Metadata / envelope which has been passed along with event

    // Following is available when isError == YES,
    // because status is PNErrorStatus instance in this case
    PNErrorStatus *errorStatus = (PNErrorStatus *)status;
    id associatedObject = errorStatus.associatedObject; // Data which may contain related information (not decrypted message for example)
    NSArray<NSString *> *erroredChannels = errorStatus.errorData.channels; // List of channels for which error reported (mostly because of PAM)
    NSArray<NSString *> *erroredChannelGroups = errorStatus.errorData.channelGroups; // List of channel groups for which error reported (mostly because of PAM)
    NSString *errorInformation = errorStatus.errorData.information; // Stringified information about error
    id errorData = errorStatus.errorData.data; // Additional error information from PubNub service
}

[self.client publish:@{ @ "msg": @"hello" } toChannel:targetChannel 
      withCompletion:^(PNPublishStatus *publishStatus) {
          if (!publishStatus.isError) {
              // Message successfully published to specified channel.
          } else {
              /**
               * Handle message publish error. Check 'category' property to find out
               * possible reason because of which request did fail.
               * Review 'errorData' property (which has PNErrorData data type) of status
               * object to get additional information about issue.
               *
               * Request can be resent using: [publishStatus retry];
               */
          }
}];

[self.client subscribeToChannels: @[@"hello-world-channel"] withPresence:YES];