Declaring publisher twice

edit

I have a program with a main.cpp and a message.cpp files.

The second has a function that is called every time an event happens and I have to send a ros message.

My first try was to declare the publisher and send the message in message.cpp:

ros::NodeHandle nh("~");
ros::Publisher pub = nh.advertise<myProject_ros::PathMessage>("/myProject_ros/message", 1000);
// creating my message
pub.publish(message);

But doing it like that, I had to insert a delay between the publisher and the publish, otherwise the listener had no time to connect.

In order to avoid introducing delays, I started creating the publisher in my main file:

ros::NodeHandle nh("~");
ros::Publisher pub = nh.advertise<myProject_ros::PathMessage>("/myProject_ros/message", 1000);

And then I wanted to publish in message.cpp:

pub.publish(message);

But then

error: ‘pub’ was not declared in this scope

So now I am creating the publisher both in the main so listener is ready and in message.cpp again to avoid pub not declared. It is working fine, I don't need delay now, but it looks like a "dirty" solution.

What is the proper way to do this? I am new to ROS and C++.