ros2 从零开始17 编写可组合节点

ros2 从零开始17 编写可组合节点前言背景之前我们提到同一个进程有多个节点这些节点之间的通信是线程同步通信基于此通信效率很高效。本节我们讨论一下可组合节点。本节也会对比之前的普通节点和组合节点的区别。起点假如我们有一个普通的节点包含main函数的。如下namespace palomino { class VincentDriver : public rclcpp::Node { // ... }; } int main(int argc, char * argv[]) { rclcpp::init(argc, argv); rclcpp::spin(std::make_sharedpalomino::VincentDriver()); rclcpp::shutdown(); return 0; }其CMakeList文件也通常如下# ... add_executable(vincent_driver src/vincent_driver.cpp) # ... install(TARGETS vincent_driver DESTINATION lib/${PROJECT_NAME} )工程更新假如要将它修改成组合节点则需要有几项修改。1. 添加包依赖package.xml应该依赖于比如rclcpp_components 所以在package.xml里面添加如下dependrclcpp_components/depend你也可以手动添加如下依赖build_depend和exec_depend2. 类定义变化类定义唯一需要改变的是需要一个带参数的构造函数如下VincentDriver(const rclcpp::NodeOptions options) : Node(vincent_driver, options) { // ... }3. 没有main函数。去掉main函数替换为下面的代码#include rclcpp_components/register_node_macro.hpp RCLCPP_COMPONENTS_REGISTER_NODE(palomino::VincentDriver)如果你的main函数使用了MultiThreadedExecutor则确保你的运行容器同样也是多线程的multithreaded。后续章节会讨论。4. CMakeList变动4.1 第一步需要添加依赖rclcpp_components如下find_package(rclcpp_components REQUIRED)4.2 第二步编译目标变化。编译目标从add_executable编译进程变成add_library编译链接库 如下add_executable已被我注释掉#add_executable(vincent_driver src/vincent_driver.cpp) add_library(vincent_driver_component SHARED src/vincent_driver.cpp)4.3 第三步替换旧目标的其他选项应用到新目标上。例如ament_target_dependencies(vincent_driver …)变成 ament_target_dependencies(vincent_driver_component rclcpp_components …) 同时别忘记了多出来的rclcpp_components。同样下面注释掉的是之前配置项未被注释的是当前使用的#ament_target_dependencies(vincent_driver tutorial_interfaces) ament_target_dependencies(vincent_driver_component tutorial_interfaces rclcpp_components)4.4 第四步添加一个声明注册你的组合节点rclcpp_components_register_node( vincent_driver_component PLUGIN palomino::VincentDriver EXECUTABLE vincent_driver )其中rclcpp_components_register_node有三个参数组合节点这里是vincent_driver_component组合节点的命名空间这里是palomino::VincentDriver组合节点名这里是vincent_driver4.5 第五步也是最后一步将CMake中运行在旧目标上的安装命令改为安装库版本。旧的安装命令注释掉的部分是将vincent_driver安装到lib/${PROJECT_NAME}目录中, 而现在的安装命令是直接安装到lib目录中。# install(TARGETS vincent_driver # DESTINATION lib/${PROJECT_NAME} # ) ament_export_targets(export_vincent_driver_component) install(TARGETS vincent_driver_component EXPORT export_vincent_driver_component ARCHIVE DESTINATION lib LIBRARY DESTINATION lib RUNTIME DESTINATION bin )运行你的节点经过上面修改后用colcon进行编译及安装这里不再赘述。关于合成节点的深入介绍请参见合成教程。按如下编写你的启动脚本。PS:根据官方教程做到运行节点时翻车了运行一直报错以为是哪里写的有问题而官方的python启动脚本又描述很少。后来看是python启动脚本的原因。这里附上的可运行的python脚本#!/usr/bin/env python3fromlaunchimportLaunchDescriptionfromlaunch_ros.actionsimportComposableNodeContainerfromlaunch_ros.descriptionsimportComposableNodefromlaunch.actionsimportExecuteProcess,TimerActionfromlaunch.substitutionsimportFindExecutabledefgenerate_launch_description():# 创建组件节点容器containerComposableNodeContainer(namemy_container,namespace,packagerclcpp_components,executablecomponent_container,composable_node_descriptions[ComposableNode(packagepalomino,pluginpalomino::VincentDriver,nameVincentDriver,extra_arguments[{use_intra_process_comms:True}]),],outputscreen,)returnLaunchDescription([container,])实际运行效果rootbc2bf85b2e4a:~/ros2_ws# ros2 launch src/palomino/launch/launch.py [INFO] [launch]: All log files can be found below /root/.ros/log/2026-04-27-06-53-18-169175-bc2bf85b2e4a-19235 [INFO] [launch]: Default logging verbosity is set to INFO [INFO] [component_container-1]: process started with pid [19247] [component_container-1] [INFO] [1777272798.537723957] [my_container]: Load Library: /root/ros2_ws/install/palomino/lib/libvincent_driver_component.so [component_container-1] [INFO] [1777272798.547384246] [my_container]: Found class: rclcpp_components::NodeFactoryTemplatepalomino::VincentDriver [component_container-1] [INFO] [1777272798.547458915] [my_container]: Instantiate class: rclcpp_components::NodeFactoryTemplatepalomino::VincentDriver [INFO] [launch_ros.actions.load_composable_nodes]: Loaded node /VincentDriver in container /my_container [component_container-1] [INFO] [1777272799.063800446] [VincentDriver]: Publishing: 0 [component_container-1] [INFO] [1777272799.563895176] [VincentDriver]: Publishing: 1 [component_container-1] [INFO] [1777272800.063988902] [VincentDriver]: Publishing: 2 [component_container-1] [INFO] [1777272800.564248809] [VincentDriver]: Publishing: 3总结可组合节点没有main函数需要通过容器或者其他的方式才能加载和运行下一章节将继续讨论其运行方式。