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the following is the code snippet, give me the right solution:
map_name_subscriber_ = this->create_subscription<std_msgs::msg::String>(
"current_map_file", 1,
GravityDirFinder::triggerFinder,
// std::bind(&GravityDirFinder::triggerFinder, this, std::placeholders::_1),
options);
void GravityDirFinder::triggerFinder()
{
// keep the robot stationary when collecting IMU data
geometry_msgs::msg::Twist zero_twist;
zero_twist.linear.x = 0.0;
zero_twist.linear.y = 0.0;
...}以下是代码片段，请给我正确的解决方案：
map_name_subscriber_ = this->create_subscription<std_msgs::msg::String>(
"current_map_file", 1、
GravityDirFinder::triggerFinder、
// std::bind(&GravityDirFinder::triggerFinder, this, std::placeholders::_1)、
选项）；
void GravityDirFinder::triggerFinder()
{
// 收集 IMU 数据时，保持机器人静止不动
几何_msgs::msg::扭曲 zeroo_twist；
zeroo_twist.linear.x = 0.0；
zeroo_twist.linear.y = 0.0；
...}
To correctly create a subscription in ROS 2 and bind it to a member function, you need to use std::bind to properly link the member function with the class instance. The line you've commented out should be used. Here is the corrected version of your code snippet:要在 ROS 2 中正确创建订阅并将其绑定到成员函数，需要使用 std::bind 将成员函数与类实例正确连接起来。应该使用你注释掉的那一行。以下是您的代码片段的更正版本：
cpp#include <functional>
#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
#include "geometry_msgs/msg/twist.hpp"
class GravityDirFinder : public rclcpp::Node
{
public:
GravityDirFinder()
: Node("gravity_dir_finder")
{
map_name_subscriber_ = this->create_subscription<std_msgs::msg::String>(
"current_map_file", 1,
std::bind(&GravityDirFinder::triggerFinder, this, std::placeholders::_1),
options);
}
private:
void triggerFinder(const std_msgs::msg::String::SharedPtr msg)
{
// keep the robot stationary when collecting IMU data
geometry_msgs::msg::Twist zero_twist;
zero_twist.linear.x = 0.0;
zero_twist.linear.y = 0.0;
zero_twist.linear.z = 0.0;
zero_twist.angular.x = 0.0;
zero_twist.angular.y = 0.0;
zero_twist.angular.z = 0.0;
// Additional code to handle the IMU data
}
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr map_name_subscriber_;
rclcpp::SubscriptionOptions options; // Initialize options if needed
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
auto node = std::make_shared<GravityDirFinder>();
rclcpp::spin(node);
rclcpp::shutdown();
return 0;
}
Key Points:要点
- Binding the Member Function: The commented-out line using
std::bindis necessary to bind the member functiontriggerFinderto the subscription callback correctly.绑定成员函数：为了将成员函数triggerFinder正确绑定到订阅回调，使用std::bind的注释行是必要的。 - Subscription Options: Ensure
optionsis properly initialized if needed. In this snippet, it is assumed to be a member variable of theGravityDirFinderclass.订阅选项：如果需要，确保options已正确初始化。在本代码段中，假定它是GravityDirFinder类的成员变量。 - Callback Parameter: The
triggerFindermethod should accept a parameter of typestd_msgs::msg::String::SharedPtrto match the message type of the subscription.回调参数：triggerFinder方法应接受std_msgs::msg::String::SharedPtr类型的参数，以匹配订阅的消息类型。
This should make the subscription work as intended, triggering the triggerFinder method when a new message is received on the current_map_file topic.这将使订阅按预期运行，在 current_map_file 主题收到新消息时触发 triggerFinder 方法。
if i wanna `triggerFInder` fucntion keep the version without arguments, how to change the map_name_subscriber_ defination如果我想让 `triggerFInder` 功能保持不带参数的版本，如何更改 map_name_subscriber_ 的定义？
If you want the triggerFinder function to remain without arguments, you can use a lambda function in the subscription definition to call triggerFinder without any arguments. Here's how you can modify your code:如果您希望 triggerFinder 函数不带参数，您可以在订阅定义中使用 lambda 函数来调用 triggerFinder 而不带任何参数。以下是修改代码的方法：
cpp#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
#include "geometry_msgs/msg/twist.hpp"
class GravityDirFinder : public rclcpp::Node
{
public:
GravityDirFinder()
: Node("gravity_dir_finder")
{
map_name_subscriber_ = this->create_subscription<std_msgs::msg::String>(
"current_map_file", 1,
[this](const std_msgs::msg::String::SharedPtr /*msg*/) {
this->triggerFinder();
},
options);
}
private:
void triggerFinder()
{
// keep the robot stationary when collecting IMU data
geometry_msgs::msg::Twist zero_twist;
zero_twist.linear.x = 0.0;
zero_twist.linear.y = 0.0;
zero_twist.linear.z = 0.0;
zero_twist.angular.x = 0.0;
zero_twist.angular.y = 0.0;
zero_twist.angular.z = 0.0;
// Additional code to handle the IMU data
}
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr map_name_subscriber_;
rclcpp::SubscriptionOptions options; // Initialize options if needed
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
auto node = std::make_shared<GravityDirFinder>();
rclcpp::spin(node);
rclcpp::shutdown();
return 0;
}
Explanation:解释：
- Lambda Function: Instead of directly binding the member function, a lambda function is used in the subscription definition. This lambda captures
this(the instance of the class) and callstriggerFinderwithout passing any arguments.lambda 函数：在订阅定义中使用 lambda 函数，而不是直接绑定成员函数。该 lambda 捕获this（类的实例）并调用triggerFinder，而不传递任何参数。 - Ignoring Message Parameter: The lambda function takes the message parameter but does not use it (
/*msg*/). This allows you to keep thetriggerFinderfunction without arguments while still fitting the expected callback signature forcreate_subscription.忽略消息参数：lambda 函数接收消息参数，但不使用它（/*msg*/）。这样，您就可以保留不含参数的triggerFinder函数，同时仍然符合create_subscription的预期回调签名。
This approach maintains the desired functionality and allows the triggerFinder method to remain argument-free.这种方法保持了所需的功能，并允许 triggerFinder 方法保持无参数状态。
how to change the code, if i also not wanna lamdba function如果我也不想使用 lamdba 功能，该如何修改代码？
If you want to avoid using a lambda function and still call triggerFinder without arguments, you can create an intermediate member function that matches the subscription callback signature and then calls triggerFinder internally. Here’s how you can achieve this:如果您想避免使用 lambda 函数，而仍然调用 triggerFinder 且不带参数，您可以创建一个与订阅回调签名相匹配的中间成员函数，然后在内部调用 triggerFinder 。下面是实现这一目的的方法：
cpp#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
#include "geometry_msgs/msg/twist.hpp"
class GravityDirFinder : public rclcpp::Node
{
public:
GravityDirFinder()
: Node("gravity_dir_finder")
{
map_name_subscriber_ = this->create_subscription<std_msgs::msg::String>(
"current_map_file", 1,
std::bind(&GravityDirFinder::mapCallback, this, std::placeholders::_1),
options);
}
private:
// Intermediate callback function
void mapCallback(const std_msgs::msg::String::SharedPtr /*msg*/)
{
this->triggerFinder();
}
void triggerFinder()
{
// keep the robot stationary when collecting IMU data
geometry_msgs::msg::Twist zero_twist;
zero_twist.linear.x = 0.0;
zero_twist.linear.y = 0.0;
zero_twist.linear.z = 0.0;
zero_twist.angular.x = 0.0;
zero_twist.angular.y = 0.0;
zero_twist.angular.z = 0.0;
// Additional code to handle the IMU data
}
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr map_name_subscriber_;
rclcpp::SubscriptionOptions options; // Initialize options if needed
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
auto node = std::make_shared<GravityDirFinder>();
rclcpp::spin(node);
rclcpp::shutdown();
return 0;
}
Explanation:解释：
- Intermediate Callback Function:
mapCallbackis created as an intermediate member function that matches the required callback signature for the subscription. It takes astd_msgs::msg::String::SharedPtrargument but does not use it.中间回调函数：mapCallback作为中间成员函数创建，它与订阅所需的回调签名相匹配。它接收std_msgs::msg::String::SharedPtr参数，但不使用该参数。 - Binding the Intermediate Function:
std::bindis used to bind themapCallbackfunction to the subscription.绑定中间函数：std::bind用于将mapCallback函数绑定到订阅。 - Calling
triggerFinder: InsidemapCallback, thetriggerFindermethod is called without arguments.调用triggerFinder：在mapCallback内部，调用triggerFinder方法时不使用参数。
This approach keeps your triggerFinder method without arguments and avoids using a lambda function in the subscription.这种方法使您的 triggerFinder 方法不含参数，并避免在订阅中使用 lambda 函数。
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