C++设计模式之状态模式(二)

2、智能空调的设计与实现

某软件公司将开发一套智能空调系统： 系统检測到温度处于20---30度之间，则切换到常温状态；温度处于30---45度，则切换到制冷状态； 温度小于20度，则切换到制热状态。

请使用状态模式对此系统进行设计。

从需求中能够看出。空调能够处于三种状态: 制热状态、常温状态、制冷状态。每种状态下都存在三种行为:保持常温、制冷、制热。

空调抽象状态实现代码例如以下:

//空调抽象状态类
class AirConditionerState
{
public:
	//保持常温
	virtual void KeepNormalTemperature(AirConditioner * pAirConditioner) = 0;

	//制冷
	virtual void refrigerate(AirConditioner * pAirConditioner) = 0;

	//制热
	virtual void Heat(AirConditioner * pAirConditioner) = 0;
};

三种详细状态类声明例如以下:

//常温状态
class NormalTemperatureState : public AirConditionerState
{
public:
	//保持常温
	void KeepNormalTemperature(AirConditioner * pAirConditioner);

	//制冷
	void refrigerate(AirConditioner * pAirConditioner);

	//制热
	void Heat(AirConditioner * pAirConditioner);
};

//制冷状态
class RefrigerateState : public AirConditionerState
{
public:
	//保持常温
	void KeepNormalTemperature(AirConditioner * pAirConditioner);

	//制冷
	void refrigerate(AirConditioner * pAirConditioner);

	//制热
	void Heat(AirConditioner * pAirConditioner);
};

//制热状态
class HeatState : public AirConditionerState
{
public:
	//保持常温
	void KeepNormalTemperature(AirConditioner * pAirConditioner);

	//制冷
	void refrigerate(AirConditioner * pAirConditioner);

	//制热
	void Heat(AirConditioner * pAirConditioner);
};

每种状态下都存在保持常温、制冷、制热方法。这些方法带有一个AirConditioner类參数，方法内部使用这个參数回调空调的温度值，依据这个温度值。用于推断该方法怎样实现。以及怎样切换到其它状态。三种状态实现代码例如以下:

/******************************正常温度状态******************************************/

//保持常温
void NormalTemperatureState::KeepNormalTemperature(AirConditioner * pAirConditioner)
{

	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature > 20 && nTemperature <= 30 )
	{
		cout << "已经是常温状态。不能调节为常温" << endl;
	}
}

//制冷
void NormalTemperatureState::refrigerate(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature > 30 && nTemperature <= 45 )
	{
		pAirConditioner->SetAirConditionerState(pAirConditioner->GetRefrigerateState());

		cout << "切换到制冷状态" << endl;
	}
}

//制热
void NormalTemperatureState::Heat(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature <= 20 )
	{
		pAirConditioner->SetAirConditionerState(pAirConditioner->GetHeatState());

		cout << "切换到制热状态" << endl;
	}
}

/******************************制冷状态******************************************/

//保持常温
void RefrigerateState::KeepNormalTemperature(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature > 20 && nTemperature <= 30 )
	{
		pAirConditioner->SetAirConditionerState(pAirConditioner->GetNormalTemperatureState());

		cout << "切换到常温状态" << endl;
	}
}

//制冷
void RefrigerateState::refrigerate(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature > 30 && nTemperature <= 45 )
	{
		cout << "已经是制冷状态，不能调节为制冷状态" << endl;
	}
}

//制热
void RefrigerateState::Heat(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature <= 20 )
	{
		pAirConditioner->SetAirConditionerState(pAirConditioner->GetHeatState());

		cout << "切换到制热状态" << endl;
	}
}

/******************************制热状态******************************************/

//保持常温
void HeatState::KeepNormalTemperature(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature > 20 && nTemperature <= 30 )
	{
		pAirConditioner->SetAirConditionerState(pAirConditioner->GetNormalTemperatureState());

		cout << "切换到常温状态" << endl;
	}
}

//制冷
void HeatState::refrigerate(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature > 30 && nTemperature <= 45 )
	{
		pAirConditioner->SetAirConditionerState(pAirConditioner->GetRefrigerateState());

		cout << "切换到制冷状态" << endl;
	}
}

//制热
void HeatState::Heat(AirConditioner * pAirConditioner)
{
	int nTemperature = pAirConditioner->GetTemperature();

	if( nTemperature <= 20 )
	{
		cout << "已经是制热状态，不能调节为制热状态" << endl;
	}
}

空调类。也就是环境类Contex,维护了一个状态的引用，实现的时候将调用状态对象的方法。声明代码例如以下:

//空调类
class AirConditioner
{
private:
	//空调名称
	string m_strAirName;

	//空调当前温度
	int m_nTemperature;

	//常温状态
	AirConditionerState * m_pNormalTemperatureState;

	//制冷状态
	AirConditionerState * m_pRefrigerateState;

	//制热状态
	AirConditionerState * m_pHeatState;

	//当前温度状态
	AirConditionerState * m_pCurState;
public:
	//构造函数
	AirConditioner(string strAirName, int nTemperature);

	//虚构函数
	~AirConditioner();

	//调节温度
	void SetTemperature(int nTemperature);

	//获取温度
	int GetTemperature();

	//设置空调状态
	void SetAirConditionerState(AirConditionerState * pAirConditionerState);

	//获取常温状态
	AirConditionerState * GetNormalTemperatureState();

	//获取制冷状态
	AirConditionerState * GetRefrigerateState();

	//获取制热状态
	AirConditionerState * GetHeatState();

	//保持常温
	void KeepNormalTemperature();

	//制冷
	void refrigerate();

	//制热
	void Heat();

};

空调类实现代码例如以下：

//构造函数
AirConditioner::AirConditioner(string strAirName, int nTemperature)
{
	m_strAirName = strAirName;
	m_nTemperature = nTemperature;

	m_pNormalTemperatureState = new NormalTemperatureState();
	m_pRefrigerateState = new RefrigerateState();
	m_pHeatState = new HeatState();

	m_pCurState = m_pNormalTemperatureState;
}

//虚构函数
AirConditioner::~AirConditioner()
{
	delete m_pNormalTemperatureState;
	m_pNormalTemperatureState = NULL;

	delete m_pRefrigerateState;
	m_pRefrigerateState = NULL;

	delete m_pHeatState;
	m_pHeatState = NULL;
}

//调节温度
void AirConditioner::SetTemperature(int nTemperature)
{
	m_nTemperature = nTemperature;
}

//获取温度
int AirConditioner::GetTemperature()
{
	return m_nTemperature;
}

//设置空调状态
void AirConditioner::SetAirConditionerState(AirConditionerState * pAirConditionerState)
{
	m_pCurState = pAirConditionerState;
}

//获取常温状态
AirConditionerState * AirConditioner::GetNormalTemperatureState()
{
	return m_pNormalTemperatureState;
}

//获取制冷状态
AirConditionerState * AirConditioner::GetRefrigerateState()
{
	return m_pRefrigerateState;
}

//获取制热状态
AirConditionerState * AirConditioner::GetHeatState()
{
	return m_pHeatState;
}

//保持常温
void AirConditioner::KeepNormalTemperature()
{
	m_pCurState->KeepNormalTemperature(this);

}

//制冷
void AirConditioner::refrigerate()
{
	m_pCurState->refrigerate(this);
}

//制热
void AirConditioner::Heat()
{
	m_pCurState->Heat(this);
}

測试代码实现例如以下:

#include <iostream>
#include "AirConditioner.h"

using namespace std;

int main()
{

	AirConditioner * pAirConditioner = new AirConditioner("海尔空调", 25);

	/****************常温状态*************************/
	pAirConditioner->KeepNormalTemperature();

	cout << endl;

	/****************制冷状态*************************/
	pAirConditioner->SetTemperature(33);
	pAirConditioner->refrigerate();

	cout << endl;

	/****************制热状态*************************/
	pAirConditioner->SetTemperature(15);
	pAirConditioner->Heat();

	/****************销毁操作*************************/
	delete pAirConditioner;
	pAirConditioner = NULL;

	return 0;
}

编译并运行，结果例如以下:

    将详细行为封装在常温状态、制冷状态、制热状态中。

空调类(也就是环境类)维持一个当前状态的引用，当client调用环境类的方法时，将该调用操作托付给详细状态类。详细状态类实现该状态下的行为，以及控制切换到其它状态。client无需直接操作详细的状态类，而是由环境类代为处理。减少了client与详细状态类的耦合性。假设须要加入详细的状态类也非常easy，仅仅须要继承于抽象状态类并对环境类稍加改动就能够了。另外。也避免了大量if...else臃肿语句。把这些条件推断都封装成一个个状态类。