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I want to read an array of integers from a file and publish them on a topic

asked 2016-03-01 01:11:30 -0500

anonymous user



 ros::Publisher publisher = nh.advertise<std_msgs::Int32MultiArray>("Topic_1",1);

  std_msgs::Int32MultiArray vec;

  int i=0;

  ifstream infile("array1.txt");
  while(infile >> temp)
      vec[i++] = temp;
      // publisher.publish(temp);
  1. > #but I'm getting this error after I run the command $catkin_make in my > workspace


    [ 85%] [ 92%] [100%] Built target subscriber
    Building CXX object task/CMakeFiles/publisher_1.dir/src/publisher_1.cpp.o
    Building CXX object task/CMakeFiles/publisher_2.dir/src/publisher_2.cpp.o
    /home/kv/krssg/src/task/src/publisher_1.cpp: In function ‘int main(int, char**)’:
    /home/kv/krssg/src/task/src/publisher_1.cpp:27:10: error: no match for ‘operator[]’ (operand types are ‘std_msgs::Int32MultiArray’ and ‘int’)
           vec[i++] = temp;
    /home/kv/krssg/src/task/src/publisher_2.cpp: In function ‘int main(int, char**)’:
    /home/kv/krssg/src/task/src/publisher_2.cpp:25:11: error: no match for ‘operator[]’ (operand types are ‘std_msgs::Int32MultiArray’ and ‘int’)
           vec2[i++] = temp;
    make[2]: *** [task/CMakeFiles/publisher_1.dir/src/publisher_1.cpp.o] Error 1
    make[1]: *** [task/CMakeFiles/publisher_1.dir/all] Error 2
    make[1]: *** Waiting for unfinished jobs....
    make[2]: *** [task/CMakeFiles/publisher_2.dir/src/publisher_2.cpp.o] Error 1
    make[1]: *** [task/CMakeFiles/publisher_2.dir/all] Error 2
    make: *** [all] Error 2
    Invoking "make -j4 -l4" failed
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1 Answer

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answered 2016-03-01 01:39:09 -0500

mgruhler gravatar image

You are trying to acces the MultiArray directly over the [] operator. Check the message definition here.

You need to do a[i++] = temp;

as, the data field is actually the vector representation. Also, make sure that the vector is big enough, so you don't get an index error. Use either the respective resize function or do push_back the new values.

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Asked: 2016-03-01 01:11:30 -0500

Seen: 338 times

Last updated: Mar 01 '16