C++有限状态机实现详解 C++有限状态机实现详解

有限状态机四大要素
C++函数指针实现
总结

前提：因为最近打算学设计模式的状态模式，但不是很明白有限状态机和状态模式之间的关系，索性用C++实现了一个简单案例复习了一下FSM，如果有更好的实现方法，欢迎留言

有限状态机四大要素

现态：当前所处状态
次态：当条件满足后，即将转移的下一个状态
动作：当满足某个事件时执行的动作；动作执行完毕后可以转移到另一个状态或保持原有状态
条件：转移状态所需的条件，当满足条件时，会触发一个动作或进行状态转移

C++函数指针实现案例：学生的日常生活。

学生的日常生活包含以下几个状态：起床、上学、吃午饭、做作业、睡觉；
每个状态之间进行转移需要执行相应的事件。

我分为以下几个步骤来实现：

（1）绘制状态转移图
（2）创建状态转移的FSMItem类
- 枚举：所有状态State、所有事件Event；
- 成员变量：现态_curState、事件_event、次态_nextState
- 成员函数：动作函数
（3）创建有限状态机FSM类
- 成员变量：状态转移表vector _fsmTable
- 成员函数：初始化状态转移表、状态转移、根据事件执行相应动作
（4）测试FSM

（1）绘制状态转移图

文章图片

（2）FSMItem类

//FSM状态项class FSMItem{friend class FSM; private://动作函数static void getUp(){cout << "student is getting up!" << endl; }static void go2School(){cout << "student is going to school!" << endl; }static void haveLunch(){cout << "student is having lunch!" << endl; }static void doHomework(){cout << "student is doing homework!" << endl; }static void sleeping(){cout << "student is sleeping!" << endl; }public://枚举所有状态enum State{GETUP = 0,GOTOSCHOOL,HAVELUNCH,DOHOMEWORK,SLEEP}; //枚举所有事件enum Events{EVENT1 = 0,EVENT2,EVENT3}; public://初始化构造函数FSMItem(State curState, Events event, void(*action)(), State nextState):_curState(curState), _event(event), _action(action), _nextState(nextState) {}private:State_curState; //现态Events_event; //条件void(*_action)(); //动作State_nextState; //次态};

（3）FSM类

class FSM{public://初始化状态机FSM(FSMItem::State curState= FSMItem::GETUP):_curState(curState){initFSMTable(); }//状态转移void transferState(FSMItem::State nextState){_curState = nextState; }//根据当前状态和发生的事件，执行相应的动作，并进行状态转移void handleEvent(FSMItem::Events event){FSMItem::StatecurState = _curState; //现态void (*action)() = nullptr; //动作FSMItem::State nextState; //次态bool flag = false; for (int i = 0; i < _fsmTable.size(); i++){if (event == _fsmTable[i]->_event && curState == _fsmTable[i]->_curState){flag = true; action = _fsmTable[i]->_action; nextState = _fsmTable[i]->_nextState; break; }}//找到对应的状态项，执行动作，转移状态if (flag){if (action){action(); }transferState(nextState); }}private://根据画的状态转移图初始化状态转移表void initFSMTable(){_fsmTable.push_back(new FSMItem(FSMItem::GETUP, FSMItem::EVENT1, &FSMItem::getUp, FSMItem::GOTOSCHOOL)); _fsmTable.push_back(new FSMItem(FSMItem::GOTOSCHOOL, FSMItem::EVENT2, &FSMItem::go2School, FSMItem::HAVELUNCH)); _fsmTable.push_back(new FSMItem(FSMItem::HAVELUNCH, FSMItem::EVENT3, &FSMItem::haveLunch, FSMItem::DOHOMEWORK)); _fsmTable.push_back(new FSMItem(FSMItem::DOHOMEWORK, FSMItem::EVENT1, &FSMItem::doHomework, FSMItem::SLEEP)); _fsmTable.push_back(new FSMItem(FSMItem::SLEEP, FSMItem::EVENT2, &FSMItem::sleeping, FSMItem::GETUP)); }public:FSMItem::State _curState; //现态private:vector _fsmTable; //状态转移表};

（4）测试FSM

#include#includeusing namespace std; //测试事件变换void testEvent(FSMItem::Events& event){switch (event){case FSMItem::EVENT1:event = FSMItem::EVENT2; break; case FSMItem::EVENT2:event = FSMItem::EVENT3; break; case FSMItem::EVENT3:event = FSMItem::EVENT1; break; }}int main(){FSM *fsm = new FSM(); auto event = FSMItem::EVENT1; while (1){cout << "event " << event << " is coming..." << endl; fsm->handleEvent(event); cout << "fsm current state is " << fsm->_curState << endl; testEvent(event); }return 0; }

执行效果：