ROS2编写一个简单的插件

1.create a base class package

ros2 pkg create --build-type ament_cmake --license Apache-2.0 --dependencies pluginlib --node-name area_node polygon_base

编辑ros2_ws/src/polygon_base/include/polygon_base/regular_polygon.hpp

#ifndef POLYGON_BASE_REGULAR_POLYGON_HPP
#define POLYGON_BASE_REGULAR_POLYGON_HPP

namespace polygon_base
{
  class RegularPolygon
  {
    public:
      virtual void initialize(double side_length) = 0;
      virtual double area() = 0;
      virtual ~RegularPolygon(){}

    protected:
      RegularPolygon(){}
  };
}  // namespace polygon_base

#endif  // POLYGON_BASE_REGULAR_POLYGON_HPP

编辑CMakeLists.txt

install(
  DIRECTORY include/
  DESTINATION include
)

ament_export_include_directories(
  include
)

2. create the plugin package

ros2 pkg create --build-type ament_cmake --license Apache-2.0 --dependencies polygon_base pluginlib --library-name polygon_plugins polygon_plugins

编辑ros2_ws/src/polygon_plugins/src/polygon_plugins.cpp

#include 
#include 

namespace polygon_plugins
{
  class Square : public polygon_base::RegularPolygon
  {
    public:
      void initialize(double side_length) override
      {
        side_length_ = side_length;
      }

      double area() override
      {
        return side_length_ * side_length_;
      }

    protected:
      double side_length_;
  };

  class Triangle : public polygon_base::RegularPolygon
  {
    public:
      void initialize(double side_length) override
      {
        side_length_ = side_length;
      }

      double area() override
      {
        return 0.5 * side_length_ * getHeight();
      }

      double getHeight()
      {
        return sqrt((side_length_ * side_length_) - ((side_length_ / 2) * (side_length_ / 2)));
      }

    protected:
      double side_length_;
  };
}

#include 
// 导出插件类
PLUGINLIB_EXPORT_CLASS(polygon_plugins::Square, polygon_base::RegularPolygon)
PLUGINLIB_EXPORT_CLASS(polygon_plugins::Triangle, polygon_base::RegularPolygon)

PLUGINLIB_EXPORT_CLASS(polygon_plugins::Square, polygon_base::RegularPolygon)
PLUGINLIB_EXPORT_CLASS(polygon_plugins::Triangle, polygon_base::RegularPolygon) 

这两行代码使用 ROS 的pluginlib库将两个类注册为插件。

Create ros2_ws/src/polygon_plugins/plugins.xml with the following code:

  
    This is a square plugin.
  
  
    This is a triangle plugin.
  

编辑ros2_ws/src/polygon_plugins/CMakeLists.txt，after the line reading find_package(pluginlib REQUIRED):

pluginlib_export_plugin_description_file(polygon_base plugins.xml)

3.使用插件

Edit ros2_ws/src/polygon_base/src/area_node.cpp

#include 
#include 

int main(int argc, char** argv)
{
  // To avoid unused parameter warnings
  (void) argc;
  (void) argv;

  pluginlib::ClassLoader poly_loader("polygon_base", "polygon_base::RegularPolygon");

  try
  {
    std::shared_ptr triangle = poly_loader.createSharedInstance("polygon_plugins::Triangle");
    triangle->initialize(10.0);

    std::shared_ptr square = poly_loader.createSharedInstance("polygon_plugins::Square");
    square->initialize(10.0);

    printf("Triangle area: %.2f\n", triangle->area());
    printf("Square area: %.2f\n", square->area());
  }
  catch(pluginlib::PluginlibException& ex)
  {
    printf("The plugin failed to load for some reason. Error: %s\n", ex.what());
  }

  return 0;
}

编译

colcon build --packages-select polygon_base polygon_plugins