动机
- 在软件构件过程中，某些对象的状态如果改变，其行为也随之发生变化
- 允许一个对象在其内部状态改变时改变它的行为，从而使对象看起来似乎修改了其行为
- State模式将所有与一个特定状态相关的行为都放入一个State的子类对象中，在对象状态切换时，切换相应的对象；但同时维持State的接口，这样实现了具体操作与状态转换之间的解耦
- 为不同的状态引入不同的对象使得状态转换变得更加明确，而且可以保证不会出现状态不一致的情况
#include class CBaseState
{
public:
CBaseState() : pNext_(nullptr) {}
virtual ~CBaseState() {}virtual void Deal() = 0;
CBaseState* GetNext() { return this->pNext_;
}protected:
CBaseState* pNext_;
};
class CState0 : public CBaseState
{
public:
virtual void Deal();
};
class CState1 : public CBaseState
{
public:
virtual void Deal();
};
class CState2 : public CBaseState
{
public:
virtual void Deal();
};
void CState0::Deal()
{
printf("State0 Deal\n");
this->pNext_ = new CState1;
}
void CState1::Deal()
{
printf("State1 Deal\n");
this->pNext_ = new CState2;
}
void CState2::Deal()
{
printf("State2 Deal\n");
delete this->pNext_;
this->pNext_ = nullptr;
}class CTest
{
public:
CTest(CBaseState* pState) : pState_(pState) {}void DealState()
{
pState_->Deal();
pState_ = pState_->GetNext();
}private:
CBaseState* pState_;
};
int main()
{
CTest Test0(new CState0);
Test0.DealState();
Test0.DealState();
Test0.DealState();
/*
State0 Deal
State1 Deal
State2 Deal
*/CTest Test1(new CState1);
Test1.DealState();
Test1.DealState();
/*
State1 Deal
State2 Deal
*/return 0;
}
【State|State 状态模式】https://www.bilibili.com/video/av24176315/?p=18
