[ROS2 Foxy] rclcpp_action “no match for ‘operator=’ (operand types are“

--- stderr: learning_action_cpp                                
/userdata/dev_ws/src/ros2_21_tutorials/learning_action_cpp/src/action_move_client.cpp: In member function ‘void MoveCircleActionClient::send_goal(bool)’:
/userdata/dev_ws/src/ros2_21_tutorials/learning_action_cpp/src/action_move_client.cpp:48:84: error: no match for ‘operator=’ (operand types are ‘rclcpp_action::Client::GoalResponseCallback’ {aka ‘std::function > >)>’} and ‘std::_Bind_helper >), MoveCircleActionClient*, const std::_Placeholder<1>&>::type’ {aka ‘std::_Bind))(std::shared_ptr >)>’})
   48 |                 std::bind(&MoveCircleActionClient::goal_response_callback, this, _1);
      |                                                                                    ^
In file included from /usr/include/c++/9/future:48,
                 from /opt/ros/foxy/include/rclcpp/executors.hpp:18,
                 from /opt/ros/foxy/include/rclcpp/rclcpp.hpp:146,
                 from /userdata/dev_ws/src/ros2_21_tutorials/learning_action_cpp/src/action_move_client.cpp:8:
/usr/include/c++/9/bits/std_function.h:462:7: note: candidate: ‘std::function<_Res(_ArgTypes ...)>& std::function<_Res(_ArgTypes ...)>::operator=(const std::function<_Res(_ArgTypes ...)>&) [with _Res = void; _ArgTypes = {std::shared_future > >}]’
  462 |       operator=(const function& __x)
      |       ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:462:33: note:   no known conversion for argument 1 from ‘std::_Bind_helper >), MoveCircleActionClient*, const std::_Placeholder<1>&>::type’ {aka ‘std::_Bind))(std::shared_ptr >)>’} to ‘const std::function > >)>&’
  462 |       operator=(const function& __x)
      |                 ~~~~~~~~~~~~~~~~^~~
/usr/include/c++/9/bits/std_function.h:480:7: note: candidate: ‘std::function<_Res(_ArgTypes ...)>& std::function<_Res(_ArgTypes ...)>::operator=(std::function<_Res(_ArgTypes ...)>&&) [with _Res = void; _ArgTypes = {std::shared_future > >}]’
  480 |       operator=(function&& __x) noexcept
      |       ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:480:28: note:   no known conversion for argument 1 from ‘std::_Bind_helper >), MoveCircleActionClient*, const std::_Placeholder<1>&>::type’ {aka ‘std::_Bind))(std::shared_ptr >)>’} to ‘std::function > >)>&&’
  480 |       operator=(function&& __x) noexcept
      |                 ~~~~~~~~~~~^~~
/usr/include/c++/9/bits/std_function.h:494:7: note: candidate: ‘std::function<_Res(_ArgTypes ...)>& std::function<_Res(_ArgTypes ...)>::operator=(std::nullptr_t) [with _Res = void; _ArgTypes = {std::shared_future > >}; std::nullptr_t = std::nullptr_t]’
  494 |       operator=(nullptr_t) noexcept
      |       ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:494:17: note:   no known conversion for argument 1 from ‘std::_Bind_helper >), MoveCircleActionClient*, const std::_Placeholder<1>&>::type’ {aka ‘std::_Bind))(std::shared_ptr >)>’} to ‘std::nullptr_t’
  494 |       operator=(nullptr_t) noexcept
      |                 ^~~~~~~~~
/usr/include/c++/9/bits/std_function.h:523:2: note: candidate: ‘template std::function<_Res(_ArgTypes ...)>::_Requires::_Callable::type>, std::function<_Res(_ArgTypes ...)>&> std::function<_Res(_ArgTypes ...)>::operator=(_Functor&&) [with _Functor = _Functor; _Res = void; _ArgTypes = {std::shared_future > >}]’
  523 |  operator=(_Functor&& __f)
      |  ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:523:2: note:   template argument deduction/substitution failed:
/usr/include/c++/9/bits/std_function.h: In substitution of ‘template template using _Requires = typename std::enable_if<_Cond::value, _Tp>::type [with _Cond = std::function > >)>::_Callable))(std::shared_ptr >)>, std::__invoke_result))(std::shared_ptr >)>&, std::shared_future > > > >; _Tp = std::function > >)>&; _Res = void; _ArgTypes = {std::shared_future > >}]’:
/usr/include/c++/9/bits/std_function.h:523:2:   required by substitution of ‘template std::function > >)>::_Requires > >)>::_Callable::type, std::__invoke_result::type&, std::shared_future > > > >, std::function > >)>&> std::function > >)>::operator=<_Functor>(_Functor&&) [with _Functor = std::_Bind))(std::shared_ptr >)>]’
/userdata/dev_ws/src/ros2_21_tutorials/learning_action_cpp/src/action_move_client.cpp:48:84:   required from here
/usr/include/c++/9/bits/std_function.h:385:8: error: no type named ‘type’ in ‘struct std::enable_if > >)>&>’
  385 |  using _Requires = typename enable_if<_Cond::value, _Tp>::type;
      |        ^~~~~~~~~
/usr/include/c++/9/bits/std_function.h:532:2: note: candidate: ‘template std::function<_Res(_ArgTypes ...)>& std::function<_Res(_ArgTypes ...)>::operator=(std::reference_wrapper<_Functor>) [with _Functor = _Functor; _Res = void; _ArgTypes = {std::shared_future > >}]’
  532 |  operator=(reference_wrapper<_Functor> __f) noexcept
      |  ^~~~~~~~
/usr/include/c++/9/bits/std_function.h:532:2: note:   template argument deduction/substitution failed:
/userdata/dev_ws/src/ros2_21_tutorials/learning_action_cpp/src/action_move_client.cpp:48:84: note:   ‘std::_Bind))(std::shared_ptr >)>’ is not derived from ‘std::reference_wrapper<_Tp>’
   48 |                 std::bind(&MoveCircleActionClient::goal_response_callback, this, _1);
      |                                                                                    ^
make[2]: *** [CMakeFiles/action_move_client.dir/build.make:63: CMakeFiles/action_move_client.dir/src/action_move_client.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:80: CMakeFiles/action_move_client.dir/all] Error 2
make: *** [Makefile:141: all] Error 2
---
Failed   <<< learning_action_cpp [9.24s, exited with code 2]
                                   
Summary: 20 packages finished [42.0s]
  1 package failed: learning_action_cpp
  1 package had stderr output: learning_action_cpp
thomas@ubuntu:/userdata/dev_ws$ 

=====================================

# Humble与Foxy版本兼容性说明

本代码仓库测试环境为：Ubuntu22.04+ROS Humble

如使用Ubuntu20.04+ROS Foxy，由于部分API接口不完全兼容，需要做一下代码修改：

## learning_action_cpp功能包


原始代码：

// 创建一个服务器收到目标之后反馈时的回调函数
void goal_response_callback(GoalHandle::SharedPtr goal_message)
{
    if (!goal_message)
    {
        RCLCPP_ERROR(this->get_logger(), "Client: Goal was rejected by server");
        rclcpp::shutdown(); // Shut down client node
    }
    else
    {
        RCLCPP_INFO(this->get_logger(), "Client: Goal accepted by server, waiting for result");
    }
}

需要更改为：

// 创建一个服务器收到目标之后反馈时的回调函数
void goal_response_callback(std::shared_future goal_message)
{
    if (!goal_message.get())
    {
        RCLCPP_ERROR(this->get_logger(), "Client: Goal was rejected by server");
        rclcpp::shutdown(); // Shut down client node
    }
    else
    {
        RCLCPP_INFO(this->get_logger(), "Client: Goal accepted by server, waiting for result");
    }
}