Hello like many this exercise for creating a custom message is a bit hard.
To be honest I have done this before but while I’m following all the steps I keep having an import error. But when I do rosmsg list | grep Age I get the correct information as shown in the examples. Now when I even copy the code form the solution and only change the package name it still won’t work.
Than I removed the Build and Devel folders but still issues, So I don’t know what to do anymore actually.
The package.xml file
<?xml version="1.0"?>
<package format="2">
<name>read_odometry_pkg</name>
<version>0.0.0</version>
<description>The read_odometry_pkg package</description>
<maintainer email="user@todo.todo">user</maintainer>
<license>TODO</license>
<buildtool_depend>catkin</buildtool_depend>
<build_depend>rospy</build_depend>
<build_depend>std_msgs</build_depend>
<build_depend>message_generation</build_depend>
<build_export_depend>rospy</build_export_depend>
<exec_depend>rospy</exec_depend>
<build_export_depend>std_msgs</build_export_depend>
<exec_depend>std_msgs</exec_depend>
<build_export_depend>message_runtime</build_export_depend>
<exec_depend>message_runtime</exec_depend>
<export>
</export>
</package>
CMakeLists
cmake_minimum_required(VERSION 2.8.3)
project(read_odometry_pkg)
## Here go all the packages needed to COMPILE the messages of topic, services and actions.
## Its only geting its paths, and not really importing them to be used in the compilation.
## Its only for further functions in CMakeLists.txt to be able to find those packages.
## In package.xml you have to state them as build
find_package(catkin REQUIRED COMPONENTS
std_msgs
message_generation
)
## Generate topic messages in the 'msg' folder
## In this function will be placed all the topic messages files of this package ( in the msg folder ) to be compiled.
add_message_files(
FILES
Age.msg
)
## Here is where the packages needed for the topic messages compilation are imported.
generate_messages(
DEPENDENCIES
std_msgs
)
## State here all the packages that will be needed by someone that executes something from your package.
## All the packages stated here must be in the package.xml as exec_depend
catkin_package(
CATKIN_DEPENDS rospy message_runtime
)
include_directories(
${catkin_INCLUDE_DIRS}
)
And the scripts I wrote
#! /usr/bin/env python
import rospy
from read_odometry_pkg import Age
rospy.init_node("publish_age_node")
pub = rospy.Publisher("/age_info", Age, queue_size=1 )
rate = rospy.Rate(2)
age = Age()
age.years = 5
age.monts = 6
age.days = 15
while not rospy.is_shutdown():
pub.publish(age)
rate.sleep()
Obviously the message file I created is called Age.msg and contains the three float32’s. I don’t see where I make any mistake here. I started first to make adjust CMakeLists and the package.xml files but when that didn’t work out well I copied it from the solution but I keep having issues.
Maybe this information helps, it is the error info:
ImportError: cannot import name ‘Age’ from ‘read_odometry_pkg’ (/home/user/catkin_ws/devel/lib/python3/dist-packages/read_odometry_pkg/init.py)
Anybody knows why?