create_pakage.md

ROS2 Creating a package

Create a package

To create a new project it is necessary to add it to a packege created in this way:

ros2 pkg create <package_name> --build-type <build_type>

• <package_name> is the name of the package
• <build_type> depend on the programming language
  • "ament_python" for Python
  • "ament_cmake" for C++

At this point will be created a folder named <package_name> in the workspace. In this folder there is another one that has the same name of the package and contains an init file: the project script has to be added in this folder.

• Python project

  It is necessary to modify the setup.py file, adding the following lines, in order to compile the project:

  entry_points={
          'console_scripts': [
            '<executable_name> = <package_name>.<script_name>:main',
          ],
  }

• C++ project

  It in necessary to modify the CMakeList in order to compile the project:

  • Add the dependencies after the standard one included by default

    # find dependencies
    find_package(ament_cmake REQUIRED)
    # uncomment the following section in order to fill in
    # further dependencies manually.
    # find_package(<dependency1> REQUIRED)
    # find_package(<dependency1> REQUIRED)

    an example of the usual nedded packages:

    # find dependencies
    find_package(ament_cmake REQUIRED)
    find_package(rclcpp REQUIRED)
    find_package(std_msgs REQUIRED)
    find_package(px4_msgs REQUIRED)
    find_package(px4_ros_com REQUIRED)

  • Add the executable files

    add_executable(<executable_file> src/<executable_file>.cpp)
    ament_target_dependencies(<executable_file> <dependencie1> <dependencie2>) 
    install(TARGETS <executable_file> DESTINATION lib/${PROJECT_NAME})

  • Add header files

    target_include_directories(<header_file> PUBLIC
      $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
      $<INSTALL_INTERFACE:include>)
    target_compile_features(<header_file> PUBLIC c_std_99 cxx_std_17)  # Require C99 and C++17

Build a project

After setting the files, build the package:

colcon build

Finally run the project:

source install/local_setup.bash
ros2 run <package_name> <executable_name>

Build clean

It is possible to clean the workspace deleting the file created building the project:

Install the colcon build if it not installed yet

sudo apt install python3-colcon-clean

Run to clean the project

colcon clean workspace