chatEvents method

Stream<QueryResult<Object?>> chatEvents(
  1. ChatId id,
  2. ChatVersion? ver,
  3. FutureOr<ChatVersion?> onVer()
)

Subscribes to ChatEvents of the specified Chat.

Authentication

Mandatory.

Initialization

Once this subscription is initialized completely, it immediately emits SubscriptionInitialized, or immediately completes (without emitting anything) if such Chat doesn't exist or MyUser doesn't participate in it.

If nothing has been emitted for a long period of time after establishing this subscription (while not being completed), it should be considered as an unexpected server error. This fact can be used on a client side to decide whether this subscription has been initialized successfully.

Result

If ver argument is not specified (or is null) an initial state of the Chat will be emitted after SubscriptionInitialized and before any other ChatEvents (and won't be emitted ever again until this subscription completes). This allows to skip doing getChat (or recentChats) before establishing this subscription.

If the specified ver is not fresh (was queried quite a time ago), it may become stale, so this subscription will return STALE_VERSION error on initialization. In such case:

  • either a fresh version should be obtained via getChat (or recentChats);
  • or a re-subscription should be done without specifying a ver argument (so the fresh ver may be obtained in the emitted initial state of the Chat).

Completion

Finite.

Completes without re-subscription necessity when:

  • The Chat does not exist (emits nothing, completes immediately after being established).
  • The authenticated MyUser is not a member of the Chat at the moment of subscribing (emits nothing, completes immediately after being established).
  • The authenticated MyUser is no longer a member of the Chat (emits EventChatItemPosted with ChatInfo of MyUser being removed and completes).

Completes requiring a re-subscription when:

  • Authenticated Session expires (SESSION_EXPIRED error is emitted).
  • An error occurs on the server (error is emitted).
  • The server is shutting down or becoming unreachable (unexpectedly completes after initialization).

Implementation

Stream<QueryResult> chatEvents(
  ChatId id,
  ChatVersion? ver,
  FutureOr<ChatVersion?> Function() onVer,
) {
  Log.debug('chatEvents($id, $ver, onVer)', '$runtimeType');

  final variables = ChatEventsArguments(id: id, ver: ver);
  return client.subscribe(
    SubscriptionOptions(
      operationName: 'ChatEvents',
      document: ChatEventsSubscription(variables: variables).document,
      variables: variables.toJson(),
    ),
    ver: onVer,
  );
}