Watch channels

You can let users watch a given channel and its messages using the Connect() method, without the need to join the channel as members.

Under the hood, this method allows your app to receive messages on a given channel by subscribing it to a message event listener underneath to receive all message events of type text. This method also returns a function you can invoke to stop receiving message events and unsubscribe from the channel.

You can use PubNub's functionality via Blueprints or directly in C++ code.

• In Blueprints, the whole SDK is managed by a subsystem, so start by initalizing the PubnubChatSubsystem node. Afterwards, you can use the Pubnub Chat object reference.

Blueprint functions

The Blueprints provided in the documentation show how you can structure your application and may contain utility methods and elements like buttons that are not part of the Unreal Chat SDK and are meant to serve as guidance.

• In C++, you can use the PubNub SDK as any other Game Instance Subsystem.

  #include "Kismet/GameplayStatics.h"
  #include "PubnubChatSubsystem.h"
  
  
  UGameInstance* GameInstance = UGameplayStatics::GetGameInstance(this);
  UPubnubChatSubsystem* PubnubChatSubsystem = GameInstance->GetSubsystem<UPubnubChatSubsystem>();
  
  
  UPubnubChat* Chat = PubnubChatSubsystem ->InitChat("demo", "demo", "my_user") // config optional

  Chat now allows you to call all Chat SDK functions, for example:

  Chat->DeleteUser("SomeUserID");

Usage in Blueprints and C++

Method signature

Blueprint

C++ / Input parameters

1Channel->Connect(FOnPubnubChannelMessageReceived MessageCallback);

* required

Parameter	Description
MessageCallback * Type: FOnPubnubChannelMessageReceived Default: n/a	Callback function passed as a parameter. It defines the custom behavior to be executed whenever someone sends a message on the given channel.

Each function in the Unreal Chat SDK that takes a callback as a parameter requires you to handle the response type accordingly.

For example, you can bind a callback function for the Channel->StreamPresence method to its handler in the following way:

1// Create a pubnub response delegate
2// you MUST implement your own callback function to handle the response
3FOnPubnubChannelStreamPresenceReceived PresenceResponse;
4PresenceResponse.BindDynamic(this, &AMyActor::OnPresenceResponseReceived);
5

6Channel->StreamPresence(PresenceResponse);

You can implement the callback function to handle the response as follows:

AMyActor.h

1UFUNCTION()
2void OnPresenceResponseReceived(const TArray<FString> &PresentUsersIDs);

AMyActor.cpp

1void AMyActor::OnPresenceResponseReceived(const TArray<FString> &PresentUsersIDs)
2{
3	for(auto PresentUser : PresentUsersIDs)
4	{
5		UE_LOG(LogTemp, Log, TEXT("Present User ID: "), *PresentUser);
6	}
7}

Handle the response

Output

This method doesn't return any value.

Sample code

Start receiving messages on the support channel.

1#include "Kismet/GameplayStatics.h"
2#include "PubnubChatSubsystem.h"
3

4UGameInstance* GameInstance = UGameplayStatics::GetGameInstance(this);
5UPubnubChatSubsystem* PubnubChatSubsystem = GameInstance->GetSubsystem<UPubnubChatSubsystem>();
6

7UPubnubChat* Chat = PubnubChatSubsystem ->InitChat("demo", "demo", "my_user");
8

9UPubnubChannel* Channel = Chat->GetChannel("support");
10

11// Create a pubnub response delegate
12// you MUST implement your own callback function to handle the response
13FOnPubnubChannelMessageReceived MessageResponse;
14MessageResponse.BindDynamic(this, &AMyActor::OnMessageResponseReceived);
15

16Channel->Connect(MessageResponse);

show all 16 lines

Other examples

Stop receiving messages on the support channel.

1Channel->Disconnect();