How to create an empty message from the publisher

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Hi,

Since publisher is tied up to single topic and topic had a fixed message datatype. Other words, given a publisher it is possible to obtain the topic name and message type. Is it possible to obtain the empty message from the publisher ?

// currently
auto chatterPub = node->create_publisher<std_msgs::msg::String>("chatter", 10);
 std_msgs::msg::String message;
 message.data = "Hello, world! "

// Looking for 
auto chatterPub = node->create_publisher<std_msgs::msg::String>("chatter", 10);
chatterMsg = ros2message(chatterPub);   // here //
chatterMsg.data = "Hello, world! "

I found this kind of interface in matlab. I am not sure how this is achieved. From publisher, topic name and topic type can be obtained as a string. But not sure hoe to convert into a datatype. Any helpful thoughts is greatly appreciated.