状态机在project中使用很的频繁，有例如以下常见的三种实现方法：

1. switch-case 实现。适合简单的状态机。

2. 二维状态表state-event实现。逻辑清晰。可是矩阵通常比較稀疏，并且维护麻烦。

3. 用状态转移表stateTransfer Table实现，数组大小等于状体转移边个数，易扩展；

以下用一个样例来进行具体说明，描写叙述的例如以下场景：

描写叙述对象：门

状态：开着、关着、锁着 (这里的关着指关了但未锁的状态)

事件：开门、关门、上锁、解锁

代码实现用枚举来定义状态和事件，操作数据节点转移到目的状态用函数实现。枚举本身默认是从0開始的int类型，利用这个特点将状态转移函数放到函数指针数组中与状态相应起来。方便操作。

核心数据结构例如以下：

状态：枚举类型

事件：枚举类型

状态转移结构体：{当前状态、事件、下个状态}，定义一个全局数组来使用

状态变更函数：到下个状态(放到数组中与状态枚举相应起来)

此种实现方法easy扩展，添加状态和事件都比較easy。

假设存在一个状态通过相应事件能够转移到多个状态的情形，则能够扩展状态转移函数。或者在状态转移结构中添加一个推断函数字段。

代码实现例如以下：

#include 
      
       using namespace std;typedef enum{    OPENED,    CLOSED,    LOCKED,}  State;typedef enum{    OPEN,    CLOSE,    LOCK,    UNLOCK} Event;typedef struct{    State currentState;    Event event;    State NextState;} StateTransfer;typedef struct{    State state;    int transferTimes;}Door;StateTransfer g_stateTransferTable[]{    {OPENED, CLOSE,  CLOSED},    {CLOSED, OPEN,   OPENED},    {CLOSED, LOCK,   LOCKED},    {LOCKED, UNLOCK, CLOSED},};void toOpen(Door& door);void toClose(Door& door);void toLock(Door& door);typedef void (*pfToState)(Door& door);pfToState g_pFun[] = {toOpen, toClose, toLock}; //状态枚举值相应下标void toOpen(Door& door){    door.state = OPENED;    cout << "open the door!\n";}void toClose(Door& door){    door.state = CLOSED;    cout << "close the door!\n";}void toLock(Door& door){    door.state = LOCKED;    cout << "lock the door!\n";}void transfer(Door& door,const Event event){    for (int i = 0; i < sizeof(g_stateTransferTable)/sizeof(StateTransfer); ++i) {        if(door.state == g_stateTransferTable[i].currentState &&           event == g_stateTransferTable[i].event){            g_pFun[g_stateTransferTable[i].NextState](door);            door.transferTimes++;            cout << "transfer ok!\n";            return;        }    }    cout << "This event cannot transfer current state!!\n";    return;}void printDoor(const Door& door){    string stateNote[] = {
     "opened","closed","locked"}; // 下标正好相应状态枚举值    cout << "the door's state is: " << stateNote[door.state] << endl;    cout << "the door transfer times is: " << door.transferTimes << endl;}int main(){    Door door = {CLOSED, 0};    printDoor(door);    transfer(door, OPEN);    printDoor(door);    transfer(door, LOCK);    printDoor(door);    transfer(door, CLOSE);    printDoor(door);    return 0;}
      

执行结果例如以下：

the door’s state is: closed

the door transfer times is: 0

open the door!

transfer ok!

the door’s state is: opened

the door transfer times is: 1

This event cannot transfer current state!!

the door’s state is: opened

the door transfer times is: 1

close the door!

transfer ok!

the door’s state is: closed

the door transfer times is: 2