Repeated Errors Despite Correct Namespace [C++] : I added a class to ns3 and when using it I keep getting the error:

    ../scratch/seven.cc: In function ‘int main(int, char**)’:
    ../scratch/seven.cc:102:3: error: ‘RandomAppHelper’ was not declared in this scope
       RandomAppHelper source = RandomAppHelper ("ns3::TcpSocketFactory", InetSocketAddress (Ipv4Address ("192.168.1.10"), 10));
       ^
    ../scratch/seven.cc:103:3: error: ‘source’ was not declared in this scope
       source.SetAttribute ("Delay", StringValue ("Constant:2.5"));
       ^
The code for this is here: **https://www.nsnam.org/docs/release/3.3/doxygen/application.html**

I can't resolve the error. I used the correct namespace ns3 in the code. Since the error is of "not declared in scope", I am not sure how to rectify it.

Please help.
