[说明]
传输门是传输系统中的重要装置。传输门具有 Open（打开）、Closed（关闭）、Opening（正在打开）、StayOpen（保持打开）、Closing（正在关闭）五种状态。触发传输门状态转 换的事件有 click、complete 和 timeout 三种。事件与其相应的状态转换如图 6-1 所示。
下面的[C++代码 1]与[C++代码 2]分别用两种不同的设计思路对传输门进行状态模拟， 请填补代码中的空缺。
[C++代码 1]
const int CLOSED = 1; const int OPENING = 2;
const int OPEN = 3; const int CLOSING = 4;
const int STAYOPEN = 5; //定义状态变量，用不同整数表示不同状态
class Door {
private:
int state; //传输门当前状态
void setState(int state){ this->state = state; } //设置当前状态
public:
Door():state(CLOSED){};
void getState(){ //根据当前状态输出相应的字符串
switch(state){
case OPENING: cout <<"OPENING" << endl; break;
case CLOSED: cout << "CLOSED" << endl; break;
case OPEN: cout << "OPEN" << endl; break;
case CLOSING: cout << "CLOSING" << endl; break;
case STAYOPEN: cout << "STAYOPEN" << endl; break;
}
}
void click() { //发生click事件时进行状态转换
if ( state==CLOSED || state==CLOSING) setState(OPENING);
else if ( state==STAYOPEN || state==OPENING) setState(CLOSING);
else if ( state=OPEN ) setState(STAYOPEN);
}
void timeout(){ //发生timeout事件时进行状态转换
if (state == OPEN) setState(CLOSING);
}
void complete(){ //发生complete事件时进行状态转换
if (state == OPENING) setState(OPEN);
else if (state == CLOSING) setState(CLOSED);
}
};
int main(){
Door aDoor;
aDoor.getState(); aDoor.click(); aDoor.getState(); aDoor.complete();
aDoor.getState(); aDoor.click(); aDoor.getState(); aDoor.click();
aDoor.getState(); return 0;
}
[C++代码 2]
class Door {
public:
DoorState *CLOSED, *OPENING, *OPEN, *CLOSING, *STAYOPEN, *state;
Door();
virtual ~Door(){ …… //释放申请的内存，此处代码省略};
void setState(DoorState *state) { this->state = state; }
void getState(){
// 此处代码省略，本方法输出状态字符串，
// 例如，当前状态为CLOSED时,输出字符串为“CLOSED”
};
void click();
void timeout();
void complete();
};
Door::Door(){
CLOSED = new DoorClosed(this); OPENING = new DoorOpening(this);
OPEN = new DoorOpen(this); CLOSING = new DoorClosing(this);
STAYOPEN = new DoorStayOpen(this); state = CLOSED;
}
void Door::click(){ state->click();}
void Door::timeout(){ state->timeout(); }
void Door::complete(){ state->complete(); }
class DoorState //定义一个抽象的状态，它是所有状态类的基类
{
protected: Door *door;
public:
DoorState(Door *door) { this->door = door; }
virtual ~DoorState(void);
virtual void click() {}
virtual void complete() {}
virtual void timeout() {}
};
class DoorClosed :public DoorState{ //定义一个基本的 Closed 状态
public:
DoorClosed(Door *door):DoorState(door) {}
virtual ~ DoorClosed (){}
void click();
};
void DoorClosed::click() { door->setState(door->OPENING); }
// 其它状态类的定义与实现代码省略
int main(){
Door aDoor;
aDoor.getState(); aDoor.click(); aDoor.getState(); aDoor.complete();
aDoor.getState(); aDoor.timeout(); aDoor.getState(); return 0;
}
