How to fetch the real data from dispatch_data_t ?

I'm using Network framework to do a simple TCP server.
When the TCP client send the data to me, nw_connection_receive handler, it give a parameter content which its type is dispatch_data_t.

I really no idea how to get the client's data from dispatch_data_t.

        nw_connection_receive(connection, 1, 256, ^(dispatch_data_t  _Nullable content, nw_content_context_t  _Nullable context, bool is_complete, nw_error_t  _Nullable error) {

            // I want to get the data which client send to me from dispatch_data_t content.

        });

Anyway, I did hate dispatch_data_t!!!!!!!!