Check out example codes for "rosrun actionlib_msgs genaction.py". It will help you in understanding the concepts better.

Code Example 1

1 #include <ros/ros.h>
   2 #include <actionlib/server/simple_action_server.h>
   3 #include <learning_actionlib/FibonacciAction.h>
   4 
   5 class FibonacciAction
   6 {
   7 protected:
   8 
   9   ros::NodeHandle nh_;
  10   actionlib::SimpleActionServer<learning_actionlib::FibonacciAction> as_; // NodeHandle instance must be created before this line. Otherwise strange error occurs.
  11   std::string action_name_;
  12   // create messages that are used to published feedback/result
  13   learning_actionlib::FibonacciFeedback feedback_;
  14   learning_actionlib::FibonacciResult result_;
  15 
  16 public:
  17 
  18   FibonacciAction(std::string name) :
  19     as_(nh_, name, boost::bind(&FibonacciAction::executeCB, this, _1), false),
  20     action_name_(name)
  21   {
  22     as_.start();
  23   }
  24 
  25   ~FibonacciAction(void)
  26   {
  27   }
  28 
  29   void executeCB(const learning_actionlib::FibonacciGoalConstPtr &goal)
  30   {
  31     // helper variables
  32     ros::Rate r(1);
  33     bool success = true;
  34 
  35     // push_back the seeds for the fibonacci sequence
  36     feedback_.sequence.clear();
  37     feedback_.sequence.push_back(0);
  38     feedback_.sequence.push_back(1);
  39 
  40     // publish info to the console for the user
  41     ROS_INFO("%s: Executing, creating fibonacci sequence of order %i with seeds %i, %i", action_name_.c_str(), goal->order, feedback_.sequence[0], feedback_.sequence[1]);
  42 
  43     // start executing the action
  44     for(int i=1; i<=goal->order; i++)
  45     {
  46       // check that preempt has not been requested by the client
  47       if (as_.isPreemptRequested() || !ros::ok())
  48       {
  49         ROS_INFO("%s: Preempted", action_name_.c_str());
  50         // set the action state to preempted
  51         as_.setPreempted();
  52         success = false;
  53         break;
  54       }
  55       feedback_.sequence.push_back(feedback_.sequence[i] + feedback_.sequence[i-1]);
  56       // publish the feedback
  57       as_.publishFeedback(feedback_);
  58       // this sleep is not necessary, the sequence is computed at 1 Hz for demonstration purposes
  59       r.sleep();
  60     }
  61 
  62     if(success)
  63     {
  64       result_.sequence = feedback_.sequence;
  65       ROS_INFO("%s: Succeeded", action_name_.c_str());
  66       // set the action state to succeeded
  67       as_.setSucceeded(result_);
  68     }
  69   }
  70 
  71 
  72 };
  73 
  74 
  75 int main(int argc, char** argv)
  76 {
  77   ros::init(argc, argv, "fibonacci");
  78 
  79   FibonacciAction fibonacci(ros::this_node::getName());
  80   ros::spin();
  81 
  82   return 0;
  83 }

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