How to read in an array with tuples from a yaml file with ROS?

Question

I have a yaml-file like this:

object_0:
  - v: 1.55
  - t_x: 110.281
  - t_y: 367.959
  - traj_const_dist: 1.0
  - trajectory: [[117, 356], [116, 356], [115, 356], [114, 356], [113, 356], [113, 357], [113, 358], [113, 359], [113, 360]]

The parameter trajectory is defined like this: std::vector<std::pair<double,double>> trajectory_;

When I read in the parameters:

ros::NodeHandle nh_;
nh_.param<std::vector<std::pair<double, double>>>(obj_topic, trajectory_, std::vector<std::pair<double, double>>());

... I get this error:

error: no matching function for call to ‘ros::NodeHandle::getParam(const string&, std::vector<std::pair<double, double> >&) const’
       if (getParam(param_name, param_val))

It would help if you give me suggestions. Is the data type std::vector<std::pair<double, double>>> not correct?

(Sorry, it is a huge project and difficult to make a small and compilable example. I will do a small one if you insist on it.)

Answer 1

It can be done by making use of XmlRpc::XmlRpcValue

Assuming the parameters in yaml file already loaded to parameter server,the following code snippet can be used:

XmlRpc::XmlRpcValue trajectory;
nh_.getParam("/param_name", trajectory);
   
/*To ensure the reading will happen if the data is provided in right format*/
if (trajectory.getType() == XmlRpc::XmlRpcValue::TypeArray)
{
    for (int i = 0; i < trajectory.size(); i++)
    {
        XmlRpc::XmlRpcValue trajectoryObject = trajectory[i];

        /*Individual coordinate points in trajectory*/

        int xCoordinate = trajectoryObject[0];
        int yCoordinate = trajectoryObject[1];
        ROS_INFO("The %d  th coordinate values are : %d and %d", ixCoordinate, yCoordinate);
    }
}