base operand of '->' has non-pointer type 'const JointState'

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Hi guys.. I am trying to write a simple publisher and subscriber, but having some problems with my subscriber...

The message type i am using is sensor_msgs::JointState msg (doc) for my subscriber i have this callback function.

void ChatterCallback(const sensor_msgs::JointState& msg){
  ROS_INFO("i've heard: " ,msg->position);
}

but somehow i end up getting this error message saying

error: base operand of '->' has non-pointer type 'const JointState'

which just doesn't make sense for me..