狀態機在工程中使用非常的頻繁，有如下常見的三種實現方法：
1. switch-case 實現，適合簡單的狀態機；
2. 二維狀態表state-event實現，邏輯清晰，但是矩陣通常比較稀疏，而且維護麻煩；
3. 用狀態轉移表stateTransfer Table實現，陣列大小等於狀體轉移邊個數，易擴充套件；
下面用一個例子來進行詳細說明，描述的如下場景：

描述物件：門
狀態：開著、關著、鎖著 (這裡的關著指關了但未鎖的狀態)
事件：開門、關門、上鎖、解鎖

程式碼實現用列舉來定義狀態和事件，操作資料節點轉移到目的狀態用函式實現。列舉本身預設是從0開始的int

狀態：列舉型別
事件：列舉型別
狀態轉移結構體：{當前狀態、事件、下個狀態}，定義一個全域性陣列來使用
狀態變更函式：到下個狀態(放到陣列中與狀態列舉對應起來)

此種實現方法容易擴充套件，增加狀態和事件都比較容易。如果存在一個狀態通過對應事件可以轉移到多個狀態的情形，則可以擴充套件狀態轉移函式，或者在狀態轉移結構中增加一個判斷函式欄位。
程式碼實現如下：

#include <iostream>
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}; //狀態列舉值對應下標

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"}; // 下標正好對應狀態列舉值
    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;
}

執行結果如下：

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