clepz's profile - activity

Hi,

I explore ros2 recently. Differences with ros, creating custom messages, pub sub examples for c++ etc.

I just wanted to demonstrate that another package can be used in a custom message.

I generated a message for simple pub-sub example. Message and its CMakefile in autodrive_msgs package :

AccelCommand.msg

float32 accel
geometry_msgs/Vector3 v

CMakefile:

cmake_minimum_required(VERSION 3.5)
project(autodrive_msgs)

# Default to C99
if(NOT CMAKE_C_STANDARD)
  set(CMAKE_C_STANDARD 99)
endif()

# Default to C++14
if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(rclcpp)
find_package(autodrive_msgs)
find_package(rosidl_default_generators REQUIRED)
rosidl_generate_interfaces(${PROJECT_NAME}
  "msg/AccelCommand.msg"
 )
# uncomment the following section in order to fill in
# further dependencies manually.
# find_package(<dependency> REQUIRED)

if(BUILD_TESTING)
  find_package(ament_lint_auto REQUIRED)
  # the following line skips the linter which checks for copyrights
  # uncomment the line when a copyright and license is not present in all source files
  #set(ament_cmake_copyright_FOUND TRUE)
  # the following line skips cpplint (only works in a git repo)
  # uncomment the line when this package is not in a git repo
  #set(ament_cmake_cpplint_FOUND TRUE)
  ament_lint_auto_find_test_dependencies()
endif()

ament_package()

I can generate the message. However It gives me a linker error when I want to use the message. Codes and CMakefile in pub_sub package:

pub.cpp:

#include <chrono>
#include <memory>

#include "rclcpp/rclcpp.hpp"
#include "autodrive_msgs/msg/accel_command.hpp"     // CHANGE

using namespace std::chrono_literals;

class MinimalPublisher : public rclcpp::Node
{
public:
  MinimalPublisher()
  : Node("minimal_publisher"), count_(0)
  {
    publisher_ = this->create_publisher<autodrive_msgs::msg::AccelCommand>("topic", 10);    // CHANGE
    timer_ = this->create_wall_timer(
      500ms, std::bind(&MinimalPublisher::timer_callback, this));
  }

private:
  void timer_callback()
  {
    auto message = autodrive_msgs::msg::AccelCommand();                               // CHANGE
    message.accel = this->count_++;                                        // CHANGE
    RCLCPP_INFO(this->get_logger(), "Publishing: '%d'", message.accel);    // CHANGE
    publisher_->publish(message);
  }
  rclcpp::TimerBase::SharedPtr timer_;
  rclcpp::Publisher<autodrive_msgs::msg::AccelCommand>::SharedPtr publisher_;         // CHANGE
  size_t count_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalPublisher>());
  rclcpp::shutdown();
  return 0;
}

sub.cpp:

#include <memory>

#include "rclcpp/rclcpp.hpp"
#include "autodrive_msgs/msg/accel_command.hpp"     // CHANGE
using std::placeholders::_1;

class MinimalSubscriber : public rclcpp::Node
{
public:
  MinimalSubscriber()
  : Node("minimal_subscriber")
  { 
    subscription_ = this->create_subscription<autodrive_msgs::msg::AccelCommand>(          // CHANGE
      "topic", 10, std::bind(&MinimalSubscriber::topic_callback, this, _1));
  }

private:
  void topic_callback(const autodrive_msgs::msg::AccelCommand::SharedPtr msg) const       // CHANGE
  {
    RCLCPP_INFO(this->get_logger(), "I heard: '%d'", msg->accel);              // CHANGE
  }
  rclcpp::Subscription<autodrive_msgs::msg::AccelCommand>::SharedPtr subscription_;       // CHANGE
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalSubscriber>());
  rclcpp::shutdown();
  return 0;
}

CMakefile:

cmake_minimum_required(VERSION 3.5)
project(pub_sub)

# Default to C99
if(NOT CMAKE_C_STANDARD)
  set(CMAKE_C_STANDARD 99)
endif()

# Default to C++14
if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

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


add_executable(talker src/pub.cpp)
ament_target_dependencies(talker rclcpp autodrive_msgs geometry_msgs)         # CHANGE

add_executable(listener src/sub.cpp)
ament_target_dependencies(listener rclcpp autodrive_msgs geometry_msgs)     # CHANGE

install(TARGETS
  talker
  listener
  DESTINATION lib/${PROJECT_NAME})

if(BUILD_TESTING)
  find_package(ament_lint_auto REQUIRED)
  # the following line skips the linter which ...