关于ros2 action发布时回调函数的模板函数格式问题

Plaech

最近在写一个c++节点需要发布目标点使用nav2导航至该目标，但是当我写到`send_goal_options.goal_response_callbac``这个回调函数时，出现了问题，编译器显示

/home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:75:172: error: no match for ‘operator=’ (operand types are ‘rclcpp_action::Client<nav2_msgs::action::NavigateToPose>::GoalResponseCallback’ {aka ‘std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>’} and ‘std::_Bind_helper<false, void (hoist_decision::*)(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >), hoist_decision*, const std::_Placeholder<1>&>::type’)
   75 | GoalHandle<nav2_msgs::action::NavigateToPose>::SharedPtr>>, this, _1 );
      |                                                                      ^

In file included from /usr/include/c++/11/functional:59,
                 from /usr/include/c++/11/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/11/algorithm:74,
                 from /home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:3:
/usr/include/c++/11/bits/std_function.h:530:9: note: candidate: ‘template<class _Functor> std::function<_Res(_ArgTypes ...)>::_Requires<std::function<_Res(_ArgTypes ...)>::_Callable<_Functor>, std::function<_Res(_ArgTypes ...)>&> std::function<_Res(_ArgTypes ...)>::operator=(_Functor&&) [with _Functor = _Functor; _Res = void; _ArgTypes = {std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >}]’
  530 |         operator=(_Functor&& __f)
      |         ^~~~~~~~
/usr/include/c++/11/bits/std_function.h:530:9: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/move.h:57,
                 from /usr/include/c++/11/bits/exception_ptr.h:43,
                 from /usr/include/c++/11/exception:153,
                 from /usr/include/c++/11/ios:39,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from /home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:1:
/usr/include/c++/11/type_traits: In substitution of ‘template<bool _Cond, class _Tp> using __enable_if_t = typename std::enable_if::type [with bool _Cond = false; _Tp = std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&]’:
/usr/include/c++/11/bits/std_function.h:353:8:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Cond, class _Tp> using _Requires = std::__enable_if_t<_Cond::value, _Tp> [with _Cond = std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::_Callable<std::_Bind<void (hoist_decision::*(hoist_decision*, std::_Placeholder<1>))(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>, std::_Bind<void (hoist_decision::*(hoist_decision*, std::_Placeholder<1>))(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>, std::__invoke_result<std::_Bind<void (hoist_decision::*(hoist_decision*, std::_Placeholder<1>))(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>&, std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > > >; _Tp = std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&; _Res = void; _ArgTypes = {std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >}]’
/usr/include/c++/11/bits/std_function.h:530:2:   required by substitution of ‘template<class _Functor> std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::_Requires<std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::_Callable<_Functor, typename std::enable_if<(! std::is_same<typename std::remove_cv<typename std::remove_reference<_Tp>::type>::type, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)> >::value), std::decay<_Tp> >::type::type, std::__invoke_result<typename std::enable_if<(! std::is_same<typename std::remove_cv<typename std::remove_reference<_Tp>::type>::type, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)> >::value), std::decay<_Tp> >::type::type&, std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > > >, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&> std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::operator=<_Functor>(_Functor&&) [with _Functor = std::_Bind<void (hoist_decision::*(hoist_decision*, std::_Placeholder<1>))(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>]’
/home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:75:172:   required from here
/usr/include/c++/11/type_traits:2205:11: error: no type named ‘type’ in ‘struct std::enable_if<false, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&>’
 2205 |     using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
      |           ^~~~~~~~~~~~~
In file included from /usr/include/c++/11/functional:59,
                 from /usr/include/c++/11/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/11/algorithm:74,
                 from /home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:3:

其中相关代码是这样的
std::bind

send_goal_options.goal_response_callback =
            std::bind(&hoist_decision::goal_response_callback<std::shared_future<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>::SharedPtr>>, this, _1 );

这个是我的回调函数

template<typename T>
    void goal_response_callback(T future)
    {
        if (debug) {
            // RCLCPP_INFO(this->get_logger(), "In task %s response callback",server_names[current_executing]);
            auto goal_handle = future.get();
            if (!goal_handle) {
            RCLCPP_ERROR(this->get_logger(), "Goal was rejected by server");
            } else {
            RCLCPP_INFO(this->get_logger(), "Goal accepted by server, waiting for result");
            }
    }
    }

看编译器中的报错，似乎是我的回调函数不对，但是我实在找不到如何改正。希望有人能给我一些意见。
顺带一提，我在CMakeList中指定了C++14来编译set(CMAKE_CXX_STANDARD 14),但是这个报错似乎显示依然是用C++11,不知道时不是这个原因。

机器人小伊

从您提供的错误信息来看，问题出在尝试将std::bind的结果赋值给rclcpp_action::Client<>::GoalResponseCallback类型的成员变量上，而std::bind返回的是一个不可转换为std::function的绑定对象（特别是当涉及到模板和完美转发时）。此外，您使用的模板函数goal_response_callback在std::bind的上下文中也没有正确地指定模板参数。

在ROS 2中，您应该使用lambda表达式来代替std::bind，因为lambda表达式与std::function的兼容性更好，并且更易于理解和使用。

这里是一个使用lambda表达式来设置goal_response_callback的例子：

send_goal_options.goal_response_callback =
    [this](std::shared_future<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>::SharedPtr> future) {
        this->goal_response_callback_helper(future);
    };

// 辅助函数，用于处理回调，避免在lambda中直接写太多代码
template<typename T>
void goal_response_callback_helper(T future) {
    if (debug) {
        // ...（您的日志代码）
        auto goal_handle = future.get();
        if (!goal_handle) {
            RCLCPP_ERROR(this->get_logger(), "Goal was rejected by server");
        } else {
            RCLCPP_INFO(this->get_logger(), "Goal accepted by server, waiting for result");
        }
    }
}

请注意，我创建了一个名为goal_response_callback_helper的辅助函数来处理实际的回调逻辑，因为lambda表达式内不适合直接写大量代码。另外，由于lambda表达式已经捕获了this指针，因此可以直接在lambda内部调用类的成员函数。

关于C++标准的问题，虽然您设置了CMAKE_CXX_STANDARD 14，但错误消息中显示的路径和错误类型通常与C++11相关。这可能是因为ROS 2的某些部分或依赖项仍然使用C++11。然而，这不太可能是您遇到的主要问题，因为lambda表达式和std::function在C++11中就已经是可用的了。

如果上述解决方案不起作用，或者您遇到其他编译错误，请检查ROS 2文档以确保您的代码与ROS 2的API兼容，并考虑升级您的ROS 2版本（如果可能的话）。

以上为生成回答，仅供参考～

Plaech

@小伊在关于ros2 action发布时回调函数的模板函数格式问题中说：

send_goal_options.goal_response_callback =
[this](std::shared_future<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>::SharedPtr> future) {
this->goal_response_callback_helper(future);
};

不对，这样修改后报错还是大同小异，不能解决我的问题

/home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:79:13: error: no match for ‘operator=’ (operand types are ‘rclcpp_action::Client<nav2_msgs::action::NavigateToPose>::GoalResponseCallback’ {aka ‘std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>’} and ‘hoist_decision::GoToPose(geometry_msgs::msg::Pose_<std::allocator<void> >::SharedPtr, int, int)::<lambda(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>’)
   79 |             };
      |             ^
In file included from /usr/include/c++/11/functional:59,
                 from /usr/include/c++/11/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/11/algorithm:74,
                 from /home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:3:
/usr/include/c++/11/bits/std_function.h:530:9: note: candidate: ‘template<class _Functor> std::function<_Res(_ArgTypes ...)>::_Requires<std::function<_Res(_ArgTypes ...)>::_Callable<_Functor>, std::function<_Res(_ArgTypes ...)>&> std::function<_Res(_ArgTypes ...)>::operator=(_Functor&&) [with _Functor = _Functor; _Res = void; _ArgTypes = {std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >}]’
  530 |         operator=(_Functor&& __f)
      |         ^~~~~~~~
/usr/include/c++/11/bits/std_function.h:530:9: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/move.h:57,
                 from /usr/include/c++/11/bits/exception_ptr.h:43,
                 from /usr/include/c++/11/exception:153,
                 from /usr/include/c++/11/ios:39,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from /home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:1:
/usr/include/c++/11/type_traits: In substitution of ‘template<bool _Cond, class _Tp> using __enable_if_t = typename std::enable_if::type [with bool _Cond = false; _Tp = std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&]’:
/usr/include/c++/11/bits/std_function.h:353:8:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Cond, class _Tp> using _Requires = std::__enable_if_t<_Cond::value, _Tp> [with _Cond = std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::_Callable<hoist_decision::GoToPose(geometry_msgs::msg::Pose_<std::allocator<void> >::SharedPtr, int, int)::<lambda(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>, hoist_decision::GoToPose(geometry_msgs::msg::Pose_<std::allocator<void> >::SharedPtr, int, int)::<lambda(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>, std::__invoke_result<hoist_decision::GoToPose(geometry_msgs::msg::Pose_<std::allocator<void> >::SharedPtr, int, int)::<lambda(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>&, std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > > >; _Tp = std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&; _Res = void; _ArgTypes = {std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >}]’
/usr/include/c++/11/bits/std_function.h:530:2:   required by substitution of ‘template<class _Functor> std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::_Requires<std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::_Callable<_Functor, typename std::enable_if<(! std::is_same<typename std::remove_cv<typename std::remove_reference<_Tp>::type>::type, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)> >::value), std::decay<_Tp> >::type::type, std::__invoke_result<typename std::enable_if<(! std::is_same<typename std::remove_cv<typename std::remove_reference<_Tp>::type>::type, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)> >::value), std::decay<_Tp> >::type::type&, std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > > >, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&> std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>::operator=<_Functor>(_Functor&&) [with _Functor = hoist_decision::GoToPose(geometry_msgs::msg::Pose_<std::allocator<void> >::SharedPtr, int, int)::<lambda(std::shared_future<std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> > >)>]’
/home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:79:13:   required from here
/usr/include/c++/11/type_traits:2205:11: error: no type named ‘type’ in ‘struct std::enable_if<false, std::function<void(std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose> >)>&>’
 2205 |     using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
      |           ^~~~~~~~~~~~~
In file included from /usr/include/c++/11/functional:59,
                 from /usr/include/c++/11/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/11/algorithm:74,
                 from /home/vr/ros2_hoist/src/hoist_decision/src/hoist_decision.cpp:3:

机器人小伊

这个错误是因为你试图将一个 lambda 表达式赋值给一个 rclcpp_action::ClientGoalHandle 类型的 std::function 回调，但是 lambda 表达式的参数类型与 std::function 所期望的参数类型不匹配。

在你的代码中，lambda 表达式是这样的：

[this](std::shared_future<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>::SharedPtr> future) {
    this->goal_response_callback_helper(future);
};

而 rclcpp_action::Client<nav2_msgs::action::NavigateToPose>::GoalResponseCallback 应该是一个接受 std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>> 的 std::function。

但是，你的 lambda 表达式中接受的是 std::shared_future 的一个模板实例，而不是直接接受 std::shared_ptr。

要修复这个错误，你需要确保 lambda 表达式的参数类型与 rclcpp_action::Client 所期望的回调类型相匹配。由于 rclcpp_action::Client 并不直接处理 std::shared_future，你应该使用一个 std::shared_ptr 而不是 std::shared_future。

如果你需要在回调函数中使用 std::shared_future（这通常不是 rclcpp_action 的标准用法），你可能需要改变你的设计，以便回调函数能够访问包含 std::shared_future 的某个对象或状态。

但是，在大多数情况下，你应该直接传递 std::shared_ptr，如下所示：

send_goal_options.goal_response_callback =
[this](std::shared_ptr<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>> goal_handle) {
    // 你的回调函数逻辑，这里可以使用 goal_handle
    this->goal_response_callback_helper(goal_handle);
};

请注意，我将 std::shared_future 替换为 std::shared_ptr<rclcpp_action::ClientGoalHandle<...>>。

确保你的 goal_response_callback_helper 函数也接受相同类型的参数。如果它确实需要 std::shared_future（这通常不是 ROS 2 actions 的情况），你需要重新设计你的代码以适应这一点。

以上为生成回答，仅供参考～

minemyemails

std::bind(&hoist_decision::goal_response_callback<std::shared_future<rclcpp_action::ClientGoalHandle<nav2_msgs::action::NavigateToPose>::SharedPtr>>, this, _1 );
这个代码的长度真是糟糕啊

Plaech

@minemyemails 确实是这样的，但是模板定义就这么长。
不过我这个错误解决不掉，改用普通函数了

小鱼

@2429148505 https://gitee.com/ohhuo/ros2bookcode/raw/master/chapt7/chapt7_ws/src/fishbot_application_cpp/src/nav2pose.cpp 可以参考这个代码

Plaech

@小鱼太好了，可惜才看到。

Plaech

@小鱼这个cookboot很好啊，之前怎么没宣传一下。之前看到你的教学中有提到一个cookbook,但好像点不进去

Plaech

@小鱼发现是新书中的代码，快快出书吧

小鱼

@2429148505 在预售了，预计8月中旬到货，等我店里上架，会更便宜点，已经要求编辑按最低价格定价了