ros msg文件数组定义与使用

float32[] ranges

注意这里的数组使用的是无长度限制的，也就是方扩号内没有东西。在使用的时候，不能够直接用数组赋值那样去做，它实际上是一个向量，往里面填充数据应使用c++中vector的push_back、resize之类的函数。参见官方教程中laserscan的发布，laserscan消息中的ranges就是这样一个向量，在程序中laserscan是使用的resize先设定容器大小，再往里填充数据的.

   1 #include <ros/ros.h>
   2 #include <sensor_msgs/LaserScan.h>
   3 
   4 int main(int argc, char** argv){
   5   ros::init(argc, argv, "laser_scan_publisher");
   6 
   7   ros::NodeHandle n;
   8   ros::Publisher scan_pub = n.advertise<sensor_msgs::LaserScan>		 ("scan", 50);
   9 
  10   unsigned int num_readings = 100;
  11   double laser_frequency = 40;
  12   double ranges[num_readings];
  13   double intensities[num_readings];
  14 
  15   int count = 0;
  16   ros::Rate r(1.0);
  17   while(n.ok()){
  18     //generate some fake data for our laser scan
  19     for(unsigned int i = 0; i < num_readings; ++i){
  20       ranges[i] = count;
  21       intensities[i] = 100 + count;
  22     }
  23     ros::Time scan_time = ros::Time::now();
  24 
  25     //populate the LaserScan message
  26     sensor_msgs::LaserScan scan;
  27     scan.header.stamp = scan_time;
  28     scan.header.frame_id = "laser_frame";
  29     scan.angle_min = -1.57;
  30     scan.angle_max = 1.57;
  31     scan.angle_increment = 3.14 / num_readings;
  32     scan.time_increment = (1 / laser_frequency) / (num_readings);
  33     scan.range_min = 0.0;
  34     scan.range_max = 100.0;
  35 
  36     ==scan.ranges.resize(num_readings);==
  37     scan.intensities.resize(num_readings);
  38     for(unsigned int i = 0; i < num_readings; ++i){
  39       scan.ranges[i] = ranges[i];
  40       scan.intensities[i] = intensities[i];
  41     }
  42 
  43     scan_pub.publish(scan);
  44     ++count;
  45     r.sleep();
  46   }
  47 }