error: expected unqualified-id before ‘(’ token when using emit event

[hoainam10th123]

when I use:

 _io->socket()->emit("join conversation", data);

If there is an error, use the following method: error: expected unqualified-id before '(' token
I have attached a photo of the error:
socket emit error
I don't understand where I went wrong. please help me.

[timurchak]

https://github.com/socketio/socket.io-client-cpp/blob/master/examples/QT/README.md