can call back based simple action client subscribe to other topics?

edit

Is it possible for a call back based simple action client to subscribe to other topics?

I want the client to subscribe to /topicA that publishes sensor_msg::JointState and pass the name, velocity, position, effort to the server.

I tried the following: (partial code): no compilation error but I'm getting segmentation fault immediately when I run the client

//client side code

sensor_msgs::JointState j_msg;   // global variable

void subCallback(const sensor_msgs::JointState::ConstPtr& msg){

    ROS_INFO("joint_name: %f",msg->position);

    j_msg.name.push_back(msg->name[0]);
    j_msg.position.push_back(msg->position[0]);
    j_msg.velocity.push_back(msg->velocity[0]);
    j_msg.effort.push_back(msg->effort[0]);

}

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

    ros::init(argc, argv, "action_client_node");

    std::string topicName = "topicA";
    ros::NodeHandle nh;

    ros::Subscriber sub = nh.subscribe(topicName,1000, subCallback);

    std::string joint_name = j_msg.name[0];
    float position = j_msg.position[0];
    float velocity = j_msg.velocity[0];
    float effort = j_msg.effort[0];

    std::cout<<"joint_name: "<<joint_name<<std::endl;
    std::cout<<"position: "<<position<<std::endl;
    std::cout<<"velocity: "<<velocity<<std::endl;
    std::cout<<"effort: "<<effort<<std::endl;

    //============================================================================================
    actionlib::SimpleActionClient<my_action::MyAction> ac_("my_action_server");
    .....
    goal.target.name.push_back(joint_name);
    goal.target.position.push_back(position);
    goal.target.velocity.push_back(velocity);
    goal.target.effort.push_back(effort);

    .....

}