What to put ROS_INFO parameter for float data type in a subscriber? [closed]

edit

Hi I'm trying to make a simple subscriber class. However I'm having an error :

error: ‘Float32’ in namespace ‘std_msgs’ does not name a type

void chatterCallback(const std_msgs::Float32::ConstPtr& msg)

Here is my code:

#include <ros/ros.h>
#include <std_msgs/Float32.h>

class FloatSub
{
private:

    ros::Publisher sub;
    std_msgs::Float32 abc;

public:
    void Callback(const std_msgs::Float32::ConstPtr& msg);
};

void FloatSub::Callback(const std_msgs::Float32::ConstPtr& msg)
{
    ROS_INFO("I heard: [%f]", msg->data);
 }

int main(int argc, char **argv)
{
  ros::init(argc, argv, "listener_class");

  ros::NodeHandle nh;

  FloatSub floatsub;
  ros::Subscriber sub = nh.subscribe("chatter", 1000, &FloatSub::Callback, &floatsub);
  ros::spin();
  return 0;
}

I think my problem comes from the line :

ROS_INFO("I heard: [%f]", msg->data);

From my understanding, since the topic is publishing a float, I also need to take in a float however I do not know how the 'msg->data' works and how it can be modified to suite different data types. If anyone could link me or any help would be welcome. Thanks.