I have a roslaunch file, in which I am including an xacro file:
<param if="$(arg load_robot_description)" name="$(arg robot_description)" command="xacro 'path/to/xacro' robot_parameters:='$(arg robot_parameters)'"/>
I now want to read some data from a json file (yaml is also possible, but json would be better), so I can pass it like shown above to the xacro and use it like
<origin xyz="$(arg robot_parameters.pose.xyz)" rpy="0 0 0"/>
in the xacro. The passing of the argument works, because if I use
<arg name="robot_parameters" default="{}"/>
it shows me that the arg gets passed to the xacro (and I get an error because it cannot access pose.xyz). Now I want to read the data from the json file and I tried multiple approaches (listed below), but none of them worked. First I tried command in arg tag
<arg name="robot_parameters" command="rosparam load $(find my_package)/robot_definition.json robot_parameters"/>
Second I tried using rosparam
<rosparam command="load" file="$(find my_package)/robot_definition.yaml" />
whereas the first marker in the yaml was called 'robot_parameters'. Third I tried using a python script:
load_json.py:
#!/usr/bin/env python3
import rospy
import json
import sys
def load_json_to_rosparam(param_name, json_file_path):
with open(json_file_path, 'r') as f:
json_data = json.load(f)
rospy.set_param(param_name, json_data)
if __name__ == '__main__':
if len(sys.argv) != 3:
sys.exit(1)
param_name = sys.argv[1]
json_file_path = sys.argv[2]
rospy.init_node('load_json_to_rosparam')
load_json_to_rosparam(param_name, json_file_path)
In the launch file:
<node name="load_json_to_rosparam_node" pkg="my_package" type="load_json.py"
args="robot_parameters $(find my_package)/robot-definition.json" output="screen" />
All of them resulted in the error "launchfile requires 'robot_parameters' to be set". What is the correct way to do this? I cannot image that it is that complicated.
