ros::init() must be called before creating a node handle

edit

If you want to control when the constructor for Z runs, you can make it a boost::shared_ptr (even a global one) and then wait until after the ros::init() before allocating it.

boost::shared_ptr<Z> z;
main()
{
  ros::init(...);
  z.reset(new Z());
  ...
}

Personally, using kind a fixed Major's version:

class ROSCommonNode
{
protected:
    ROSCommonNode(int argc, char **argv, const char *node_name)
    {
        ros::init(argc, argv, node_name);
    }
};

class ROSCommonWorker : ROSCommonNode
{
public:
    ROSCommonWorker(int argc, char **argv, const char *node_name) : ROSBaseNode(argc, argv, node_name)
    {
        //register some common publishers/subscribers or deal with global param service, whatever
    }

private:
    ros::NodeHandle node_handle;
};

Motivation: couple of duplicated lines of code saved, also centralized way of changing how all of my common nodes/services/workers/etc. works with logging/dealing with parameters/etc.

I have done it in this way

class Rosinit
{
    static int is_inited = 0;
public:
    Rosinit(int argc, char **argv, const char *node_name)
    {
        if(!is_inited){

        ros::init(argc,argv,node_name);
        is_inited=1;
        }
    }
};


class Rosnode_parent
{

    Rosinit init;
public:
    ros::NodeHandle n;

    Rosnode_parent(int argc, char **argv, const char *node_name):init(argc, argv, node_name)
    {
       //...
    };
};

the class Rosnode_parent has a memer Rosinit init, in the constructer this member is initializied with with an argumentlist,this is done bevor a NodeHandle Construkter is called.

in class Rosinit the static member "static int is_inited" enusres that there is only on call of ros::init

I use Rosnode_parent as a super calls and inherite , important is that in the childclass in there own constructer the super constructer is called

In my case it was because I was trying to launch a ROS2 launch in a terminal session that has previously ROS1 sourcing. To solve it be sure to ONLY source ROS related stuff: source /opt/ros/foxy/setup.bash, and colcon build from scratch your workspace just in case.