三、基于面向对象的FSM实现技术
3.1、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);
}
