Developing a ROS 2 package
This tutorial will teach you how to create your first ROS 2 application. It is intended for developers who want to learn how to create custom packages in ROS 2, not for people who want to use ROS 2 with its existing packages.
Prerequisites
Setup your workspace by sourcing your ROS 2 installation.
Creating a package
All ROS 2 packages begin by running the command
ros2 pkg create --license Apache-2.0 <pkg-name> --dependencies [deps]
in your workspace (usually ~/ros2_ws/src
).
To create a package for a specific client library:
ros2 pkg create --build-type ament_cmake --license Apache-2.0 <pkg-name> --dependencies [deps]
ros2 pkg create --build-type ament_python --license Apache-2.0 <pkg-name> --dependencies [deps]
You can then update the package.xml
with your package info such as dependencies, descriptions, and authorship.
C++ Packages
You will mostly use the add_executable()
CMake macro along with
ament_target_dependencies(<executable-name> [dependencies])
to create executable nodes and link dependencies.
To install your launch files and nodes, you can use the install()
macro placed towards the end of the file but before the ament_package()
macro.
An example for launch files and nodes:
# Install launch files
install(
DIRECTORY launch
DESTINATION share/${PROJECT_NAME}
)
# Install nodes
install(
TARGETS [node-names]
DESTINATION lib/${PROJECT_NAME}
)
Python Packages
ROS 2 follows Python’s standard module distribution process that uses setuptools
.
For Python packages, the setup.py
file complements a C++ package’s CMakeLists.txt
.
More details on distribution can be found in the official documentation.
In your ROS 2 package, you should have a setup.cfg
file which looks like:
[develop]
script_dir=$base/lib/<package-name>
[install]
install_scripts=$base/lib/<package-name>
and a setup.py
file that looks like:
import os
from glob import glob
from setuptools import setup
package_name = 'my_package'
setup(
name=package_name,
version='0.0.0',
# Packages to export
packages=[package_name],
# Files we want to install, specifically launch files
data_files=[
# Install marker file in the package index
('share/ament_index/resource_index/packages', ['resource/' + package_name]),
# Include our package.xml file
(os.path.join('share', package_name), ['package.xml']),
# Include all launch files.
(os.path.join('share', package_name, 'launch'), glob(os.path.join('launch', '*.launch.py'))),
],
# This is important as well
install_requires=['setuptools'],
zip_safe=True,
author='ROS 2 Developer',
author_email='ros2@ros.com',
maintainer='ROS 2 Developer',
maintainer_email='ros2@ros.com',
keywords=['foo', 'bar'],
classifiers=[
'Intended Audience :: Developers',
'License :: TODO',
'Programming Language :: Python',
'Topic :: Software Development',
],
description='My awesome package.',
license='TODO',
# Like the CMakeLists add_executable macro, you can add your python
# scripts here.
entry_points={
'console_scripts': [
'my_script = my_package.my_script:main'
],
},
)
Combined C++ and Python Packages
When writing a package with both C++ and Python code, the setup.py
file and setup.cfg
file are not used.
Instead, use ament_cmake_python.