How to use parameters

Declare and use parameters in the constructor of the node like this:

self.declare_parameter("some_name", "default_value")
self.my_value = self.get_parameter("some_name").value

this->declare_parameter("some_name", 100);
int my_value = this->get_parameter("some_name").as_int();

Set the parameters during runtime:

ros2 run my_pkg my_node --ros-args -p some_name:=the_value

The type of the value will be automatically interpreted by ROS2 - int, string, double and so on.

List and get the parameters during runtime:

ros2 param list

ros2 param get /the_node the_param