FSM(finite state machine)

基于面向对象的FSM实现技术

                       ——用一个类实现FSM

 
 

class DoorFSM {

private:
   States __Y;
   std::queue<Event> __events;
   void __processEvent( Event e );
 
protected:
   virtual void enterOpened() = 0;
   virtual void enterLocked() = 0;
   virtual void enterUnlocked() = 0;
   virtual void enterClosed() = 0;
public:
/* States */
   enum States { Closed, Unlocked, Locked, Opened   }; // states
/*Events*/
   enum Event { Lock, Unlock, Open, Close   };
   /// Constructor
   DoorFSM() { __Y = Opened; }
   /// Destructor
   virtual ~DoorFSM() {}
 
   /** Get current FSM state
       @returns current FSM state
    */
   States currentState() { return __Y; }
 
   /** Send event to FSM
       Use this function to send event to DoorFSM After you call it given event will be handled, and, if some of transition conditions match, appropriate transition will be triggered, and currentState() will be changed. If this function is called during existing event handling process, given event will be added to pending event queue, and will be handled after current transition. See examples for details.
   */
   void A( Event e );
};

void DoorFSM::__processEvent( Event e )

{

   States yOld = __Y;

   bool pass = false;

   switch( __Y ) { //transitions

   case Closed:

      if( e == Open ) {

         //outcome actions

         __Y = Opened;

         pass = true;

      }

      else if( e == Lock ) {

         //outcome actions

         __Y = Locked;

         pass = true;

      }

      break;

   case Unlocked:

      if( e == Lock ) {

         //outcome actions

         __Y = Locked;

         pass = true;

      }

      else if( e == Open ) {

         //outcome actions

         __Y = Opened;

         pass = true;

      }

      break;

   case Locked:

      if( e == Unlock ) {

         //outcome actions

         __Y = Unlocked;

         pass = true;

      }

      break;

   case Opened:

      if( e == Close ) {

         //outcome actions

         __Y = Closed;

         pass = true;

      }

      break;

   }

 

   if( yOld == __Y && !pass ) { return; }

 

   switch( __Y ) { // income actions

   case Closed:

         enterClosed();

      break;

   case Unlocked:

         enterUnlocked();

      break;

   case Locked:

         enterLocked();

      break;

   case Opened:

         enterOpened();

      break;

   }

}

 

void DoorFSM::A( Event e )

{

   bool __empty = __events.empty();

   __events.push( e );

   if( __empty ) {

      while( !__events.empty() ) {

         __processEvent( __events.front() );

         __events.pop();

      }

   }

}

 

 

class DoorFSMLogic : public DoorFSM
{
 protected:
  virtual void enterOpened(){std::cout << "Enter Opened state." << std::endl;}

  virtual void enterLocked() {std::cout << "Enter Closed state." << std::endl;}
  virtual void enterUnlocked() {std::cout << "Enter Locked state." << std::endl;}
  virtual void enterClosed() {std::cout << "Enter Unlocked state." << std::endl;}
};

测试程序

int main()
{
  DoorFSMLogic door;
  door.A(DoorFSM::Close);
  door.A(DoorFSM::Lock);
  door.A(DoorFSM::Unlock);
  door.A(DoorFSM::Open);
}