dart .. 점두개

final client = StreamChatClient(
      apiKey ?? streamApiKey,
    );
    
client.chatPersistenceClient = chatPersistentClient;

위와 아래는 같습니다. 코드를 간결히 할 수 있네요.

final client = StreamChatClient(
      apiKey ?? streamApiKey,
    )..chatPersistenceClient = chatPersistentClient;