设计模式之State状态模式

class State
{
public:
	virtual ~State() = default;
	virtual void display() = 0;

protected:
	State() = default;

private:
};

class NormalState : public State
{
public:
	NormalState()
	{
		std::cout << "NormalState 构造函数" << std::endl;
	}

	~NormalState() override
	{
		std::cout << "~NormalState 析构函数" << std::endl;
	}

	void display() override
	{
		std::cout << "正常大小" << std::endl;
	}

private:
};

class DoubleState : public State
{
public:
	DoubleState()
	{
		std::cout << "DoubleState 构造函数" << std::endl;
	}

	~DoubleState() override
	{
		std::cout << "~DoubleState 析构函数" << std::endl;
	}

	void display() override
	{
		std::cout << "两倍大小" << std::endl;
	}

private:
};

class QuadrupleState : public State
{
public:
	QuadrupleState()
	{
		std::cout << "QuadrupleState 构造函数" << std::endl;
	}

	~QuadrupleState() override
	{
		std::cout << "~QuadrupleState 析构函数" << std::endl;
	}

	void display() override
	{
		std::cout << "四倍大小" << std::endl;
	}

private:
};

//枚举型
enum ScreenState
{
	normal_state,	//正常状态
	double_state,   //两倍放大状态
	quadruple_state	//四倍放大状态
};


//Screen
class Screen
{
public:
	Screen()
	{
		m_ScreenState = ScreenState::nromal_state;

		m_eNormalState = new NormalState();
		m_eDoubleState = new DoubleState();
		m_eQuadrupleState = new QuadrupleState();
	}
	~Screen()
	{
		delete m_eNormalState;
		delete m_eDoubleState;
		delete m_eQuadrupleState;
	}
	void onClick()
	{
		std::cout << "点击一下，";

		if (m_ScreenState == ScreenState::normal_state)
		{
			m_eDoubleState->display();
			setState(ScreenState::double_state);
		}
		else if (m_ScreenState == ScreenState::double_state){
			m_eQuadrupleState->display();
			setState(ScreenState::quadruple_state);
		}
		else if (m_ScreenState == ScreenState::quadruple_state) {
			m_eNormalState->display();
			setState(ScreenState::nromal_state);
		}
	}
private:
	void setState(const ScreenState state)
	{
		this->m_ScreenState = state;
	}

private:
	State *m_eNormalState;
	State *m_eDoubleState;
	State *m_eQuadrupleState;

	ScreenState m_ScreenState;
};

#include 
#include 
#include 
using namespace std;

int main()
{
	std::cout << "==环境类来负责状态之间的转换==" << std::endl;
	std::cout << "初始" << std::endl;
	auto *screen = new Screen();
	std::cout << "点击 click 测试" << std::endl;
	screen->onClick();
	screen->onClick();
	screen->onClick();
	screen->onClick();
	screen->onClick();
	delete screen;

	getchar();

	return 0;
}

//状态类中引用了Screen类，所以必须提前声明
class Screen;

class State
{
public:
	virtual ~State() = default;
	virtual void changeState(Screen *screen) = 0;
	virtual void display() = 0;

protected:
	State() = default;

private:
};

//
class NormalState : public State
{
public:
	NormalState()
	{
		std::cout << "NormalState 构造函数" << std::endl;
	}

	~NormalState() override
	{
		std::cout << "~NormalState 析构函数" << std::endl;
	}

    
	void changeState(Screen *screen) override;

	void display() override
	{
		std::cout << "正常大小" << std::endl;
	}

private:
};

//
class DoubleState : public State
{
public:
	DoubleState()
	{
		std::cout << "DoubleState 构造函数" << std::endl;
	}

	~DoubleState() override
	{
		std::cout << "~DoubleState 析构函数" << std::endl;
	}
    
    
	void changeState(Screen *screen) override;

	void display() override
	{
		std::cout << "两倍大小" << std::endl;
	}

private:
};

//
class QuadrupleState : public State
{
public:
	QuadrupleState()
	{
		std::cout << "QuadrupleState 构造函数" << std::endl;
	}

	~QuadrupleState() override
	{
		std::cout << "~QuadrupleState 析构函数" << std::endl;
	}

    
	void changeState(Screen *screen) override;

	void display() override
	{
		std::cout << "四倍大小" << std::endl;
	}

private:
};

//枚举型
enum ScreenState
{
	normal_state,	//正常状态
	double_state,   //两倍放大状态
	quadruple_state	//四倍放大状态
};

//Context（上下文）:Screen
class Screen
{
public:
	Screen()
	{
		m_ScreenState = ScreenState::normal_state;

		m_pCurrentState = nullptr;
		m_pNormalState = new NormalState();
		m_pDoubleState = new DoubleState();
		m_pQuadrupleState = new QuadrupleState();

		//必须调用，相当于给m_pCurrentState初始化
		setState(ScreenState::normal_state);
	}
	~Screen()
	{
		delete m_pNormalState;
		delete m_pDoubleState;
		delete m_pQuadrupleState;
	}
	void onClick()
	{
		std::cout << "点击一下，";
		m_pCurrentState->changeState(this);
	}
	void setState(const ScreenState &state)
	{
		this->m_ScreenState = state;

		if (m_ScreenState == ScreenState::normal_state)
		{
			m_pCurrentState = m_pNormalState;
		}
		else if (m_ScreenState == ScreenState::double_state) {
			m_pCurrentState = m_pDoubleState;
		}
		else if (m_ScreenState == ScreenState::quadruple_state) {
			m_pCurrentState = m_pQuadrupleState;
		}
	}

private:
	State *m_pCurrentState;

	State *m_pNormalState;
	State *m_pDoubleState;
	State *m_pQuadrupleState;

	ScreenState m_ScreenState;
};

 ConcreteState（具体状态类）中changeState必须放在Screen类之后实现：

void NormalState::changeState(Screen *screen)
{
	display();
	screen->setState(ScreenState::double_state);
}

void DoubleState::changeState(Screen *screen)
{
	display();
	screen->setState(ScreenState::quadruple_state);
}

void QuadrupleState::changeState(Screen *screen)
{
	display();
	screen->setState(ScreenState::normal_state);
}

#include 
#include 
#include 
using namespace std;

int main()
{
	std::cout << "==由具体状态类来负责状态之间的转换==" << std::endl;
	std::cout << "初始" << std::endl;
	auto *screen = new Screen();
	std::cout << "点击 click 测试" << std::endl;
	screen->onClick();
	screen->onClick();
	screen->onClick();
	screen->onClick();
	screen->onClick();
	delete screen;

	getchar();

	return 0;
}