ROS回调函数传参

一、回调函数仅含单个参数

C++ 代码
void chatterCallback(const std_msgs::String::ConstPtr& msg)  
{  
  ROS_INFO("I heard: [%s]", msg->data.c_str());  
}  
int main(int argc, char** argv)
{
  ....
  ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback); 
  ....
}

#python代码，简要示例
def callback(data):
    rospy.loginfo("I heard %s",data.data)
    
def listener():
    rospy.init_node('node_name')
    rospy.Subscriber("chatter", String, callback)
    # spin() simply keeps python from exiting until this node is stopped
    rospy.spin()

C++ 解析图像
#include 
#include 
#include 
#include 
#include 
#include 
#include

using namespace std;
using namespace cv;


long int count_ =0000;//不能命名成count
int n=0;
void imageCallback(const sensor_msgs::ImageConstPtr& msg)
{
      cv_bridge::CvImagePtr cv_ptr;
      try   //对错误异常进行捕获，检查数据的有效性
        { 
         cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::BGR8);
         char base_name[256];
         if(n%10==0)
         {
         sprintf(base_name,"/home/zhy/Documents/data/%04ld.jpg",count_++);
         imwrite(base_name, cv_ptr->image);
         }
         n++;
        }
        catch(cv_bridge::Exception& e)  //异常处理
        {
            ROS_ERROR("cv_bridge exception: %s", e.what());
            return;
        }    
        
}

int main(int argc, char** argv)
{
  ros::init(argc, argv, "msg2img2");
  ros::NodeHandle nh_;
  ros::Subscriber image_sub_ = nh_.subscribe("/pylon_camera_node/image_raw", 1, imageCallback);///middle/pylon_camera_node/image_raw/compressed
  
  ros::spin();
  return 0;
}

二、回调函数含有多个参数

#C++代码
void chatterCallback(const std_msgs::String::ConstPtr& msg，type1 &arg1, type2 &arg2,...,typen &argN)  
{  
  ROS_INFO("I heard: [%s]", msg->data.c_str());  
}  
int main(int argc, char** argv)
{
  ros::Subscriber sub = 
      n.subscribe("chatter", 1000, boost::bind(&chatterCallback,_1,arg1,arg2,...,argN); 
  ///需要注意的是，此处  _1 是占位符， 表示了const std_msgs::String::ConstPtr& msg。
}

#python代码,python中使用字典
def callback(data, args): 
  dict_1 = args[0]
  dict_2 = args[1]
... 

sub = rospy.Subscriber("text", String, callback, (dict_1, dict_2))

#include 
#include 
#include 
#include 
#include 
#include 
#include

using namespace std;
using namespace cv;


long int count_ =0000;//不能命名成count
int n=0;
void imageCallback(const sensor_msgs::ImageConstPtr& msg, int &rp,char* &ip, int &up)
{
      cv_bridge::CvImagePtr cv_ptr;
      try   //对错误异常进行捕获，检查数据的有效性
        { 
         cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::BGR8);
         char base_name[256];
         if(n%10==0)
         {
         sprintf(base_name,"/home/zhy/Documents/data/%04ld.jpg",count_++);
         imwrite(base_name, cv_ptr->image);
         }
         n++;
        }
        catch(cv_bridge::Exception& e)  //异常处理
        {
            ROS_ERROR("cv_bridge exception: %s", e.what());
            return;
        }    
        
}

int main(int argc, char** argv)
{

  int rtp=3;
 char IP[40]="127.0.0.1";
 int udp=4;
  
  ros::init(argc, argv, "msg2img2");
  ros::NodeHandle nh_;
  
  ros::Subscriber image_sub_ = nh_.subscribe("/pylon_camera_node/image_raw", 1,
                                               boost::bind(&imageCallback, _1, rtp,IP,udp)); 

  ros::spin();
  return 0;
}

三、boost::bind()

boost::bind支持所有的function object, function, function pointer以及member function pointers，能够将行数形参数绑定为特定值或者调用所需要的参数，并可以将绑定的参数分配给任意形参。

boost::bind()的使用方法(functions and function pointers)

定义如下函数：

int f(int a, int b)
{
    return a + b;
}

bind(f,_1,5)(x)相当于f(x,5)；_1是一个占位符，其位于f函数形参的第一形参int a的位置，5位于f函数形参int b的位置；_1表示(x)参数列表的第一个参数