title: boost::msm usage: how to set properties of target states
body: <p>States in my fsm has different properties. I define a event which will invoke a transition to a target state. I want to set properties of target by event data. My choices are:
  1. set properties in the action or guard: but it is still in the source state. I fill not good if i set the target state properties at the time
  2. set properties in the target entry: but the value of properties have been calculated in guard on receiving the event so i should recalculated again :(</p>
  
  <p>Any one can give me more ideas. Thanks ! </p>