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爱装网,青岛seo软件,怎么登录别人的wordpress,网站开发建设付款方式状态模式概述状态模式是一种行为型设计模式，它可以让一个对象在其内部状态发生变化时更改其行为。通过将每个状态封装成一个独立的类，我们可以使状态之间互相独立，并且使得状态的切换变得更加灵活、可扩展。（多个状态之间可以相…

状态模式概述

状态模式是一种行为型设计模式，它可以让一个对象在其内部状态发生变化时更改其行为。通过将每个状态封装成一个独立的类，我们可以使状态之间互相独立，并且使得状态的切换变得更加灵活、可扩展。（多个状态之间可以相互转换）
在状态模式中，我们通常会定义一个抽象状态类（Abstract State），以及多个具体状态类（Concrete States）。每个具体状态都会实现抽象状态类中定义的各种操作，并且在需要时执行状态转换。
此外，还有一个环境类（Context），它包含了当前状态，并且在状态发生变化时调用各个状态类的方法来实现状态转换。因为这些状态类都实现了同一个接口，所以环境类不需要知道具体状态的细节，只需要调用相应的方法即可。

如何理解状态类和环境类

电视遥控器	人
开电视	学习
关电视	睡觉
静音	打游戏

电视遥控器的例子

一个电视遥控器。电视遥控器有三种状态：开机状态、关机状态和静音状态。我们可以通过简单地按遥控器上的按钮来更改状态。为了实现这个功能，首先我们需要定义一个抽象状态类，该类将定义所有可能的操作：

class TVState {
public:virtual void onButtonPressed(TVRemote* remote) = 0;virtual void offButtonPressed(TVRemote* remote) = 0;virtual void muteButtonPressed(TVRemote* remote) = 0;
};

TVState中包含了三种操作：开机、关机和静音。这些操作在不同的状态下可能会有不同的实现方式，因此我们需要在具体状态类中进行实现。

// 具体状态类：开机状态
class OnState : public TVState {
public:void onButtonPressed(TVRemote* remote) override {std::cout << "The TV is already on." << std::endl;}void offButtonPressed(TVRemote* remote) override {std::cout << "Turning off the TV." << std::endl;remote->setState(new OffState());}void muteButtonPressed(TVRemote* remote) override {std::cout << "Muting the TV." << std::endl;remote->setState(new MuteState());}
};// 具体状态类：关机状态
class OffState : public TVState {
public:void onButtonPressed(TVRemote* remote) override {std::cout << "Turning on the TV." << std::endl;remote->setState(new OnState());}void offButtonPressed(TVRemote* remote) override {std::cout << "The TV is already off." << std::endl;}void muteButtonPressed(TVRemote* remote) override {std::cout << "Cannot mute the TV when it's turned off." << std::endl;}
};// 具体状态类：静音状态
class MuteState : public TVState {
public:void onButtonPressed(TVRemote* remote) override {std::cout << "Unmuting the TV." << std::endl;remote->setState(new OnState());}void offButtonPressed(TVRemote* remote) override {std::cout << "Turning off the TV." << std::endl;remote->setState(new OffState());}void muteButtonPressed(TVRemote* remote) override {std::cout << "The TV is already muted." << std::endl;}
};

在这些具体状态类中，我们重写了TVState中定义的所有操作，并且在需要时执行状态转换。例如，在开机状态下按下静音键会将遥控器的状态更改为“静音状态”。
接下来，让我们定义环境类（Context）：

class TVRemote {
private:TVState* currentState;public:TVRemote() {currentState = new OffState();}void setState(TVState* state) {currentState = state;}void pressOnButton() {currentState->onButtonPressed(this);}void pressOffButton() {currentState->offButtonPressed(this);}void pressMuteButton() {currentState->muteButtonPressed(this);}
};

在环境类中，我们维护了当前状态，并且在状态发生变化时调用相应的具体状态类方法。我们还定义了三个按键操作：开机、关机和静音。
现在，我们可以使用电视遥控器来测试状态模式的实现了：

int main() {TVRemote remote;remote.pressOnButton();    // Turning on the TV.remote.pressOnButton();    // The TV is already on.remote.pressMuteButton();  // Muting the TV.remote.pressMuteButton();  // The TV is already muted.remote.pressOffButton();   // Turning off the TV.remote.pressOffButton();   // The TV is already off.remote.pressMuteButton();  // Cannot mute the TV when it's turned off.remote.pressOnButton();    // Turning on the TV.remote.pressMuteButton();  // Unmuting the TV.return 0;
}

通过上面的代码，我们可以看到当我们按下不同的键时，电视遥控器的状态会发生相应的变化。

完整代码

remote.cpp

#include "remote.h"
#include "state.h"TVRemote::TVRemote(TVState* State )
{currentState = State;
}void TVRemote::setState(TVState* state)
{currentState = state;
}void TVRemote::pressOnButton()
{currentState->onButtonPressed(this);
}void TVRemote::pressOffButton()
{currentState->offButtonPressed(this);
}void TVRemote::pressMuteButton()
{currentState->muteButtonPressed(this);
}

remote.h

#pragma once
class TVState; //这里没声明，报了一堆错class TVRemote
{
private:TVState* currentState;public:TVRemote(TVState* State);void setState(TVState* state);void pressOnButton();void pressOffButton();void pressMuteButton();
};

state.h

#pragma once
#include"remote.h"class TVState {
public:virtual void onButtonPressed(TVRemote* remote) = 0; // 开机virtual void offButtonPressed(TVRemote* remote) = 0; // 关机virtual void muteButtonPressed(TVRemote* remote) = 0; // 静音
};// 具体状态类：关机状态
class OffState : public TVState
{
public:void onButtonPressed(TVRemote* remote) override;void offButtonPressed(TVRemote* remote) override;void muteButtonPressed(TVRemote* remote) override;
};// 具体状态类：开机状态
class OnState : public TVState
{
public:void onButtonPressed(TVRemote* remote) override;void offButtonPressed(TVRemote* remote) override;void muteButtonPressed(TVRemote* remote) override;
};// 具体状态类：静音状态
class MuteState : public TVState {
public:void onButtonPressed(TVRemote* remote) override;void offButtonPressed(TVRemote* remote) override;void muteButtonPressed(TVRemote* remote) override;
};

state.cpp

#include<iostream>
#include "state.h"
#include "remote.h"// 具体状态类：关机状态
void OffState::onButtonPressed(TVRemote* remote) 
{std::cout << "Turning on the TV." << std::endl;remote->setState(new OnState());
}void OffState::offButtonPressed(TVRemote* remote) 
{std::cout << "The TV is already off." << std::endl;
}void OffState::muteButtonPressed(TVRemote* remote)
{std::cout << "Cannot mute the TV when it's turned off." << std::endl;
}// 具体状态类：开机状态
void OnState::onButtonPressed(TVRemote* remote) 
{std::cout << "The TV is already on." << std::endl;
}void OnState::offButtonPressed(TVRemote* remote) 
{std::cout << "Turning off the TV." << std::endl;remote->setState(new OffState());
}void OnState::muteButtonPressed(TVRemote* remote)
{std::cout << "Muting the TV." << std::endl;remote->setState(new MuteState());
}// 具体状态类：静音状态
void MuteState::onButtonPressed(TVRemote* remote)
{std::cout << "Unmuting the TV." << std::endl;remote->setState(new OnState());
}void MuteState::offButtonPressed(TVRemote* remote) 
{std::cout << "Turning off the TV." << std::endl;remote->setState(new OffState());
}void MuteState::muteButtonPressed(TVRemote* remote)
{std::cout << "The TV is already muted." << std::endl;
}

main.cpp

#include <iostream>
using namespace std;
#include "state.h"
#include "remote.h"int main() {TVState* off = new MuteState;TVRemote remote(off);remote.pressOnButton();    // Turning on the TV.remote.pressOnButton();    // The TV is already on.remote.pressMuteButton();  // Muting the TV.remote.pressMuteButton();  // The TV is already muted.remote.pressOffButton();   // Turning off the TV.remote.pressOffButton();   // The TV is already off.remote.pressMuteButton();  // Cannot mute the TV when it's turned off.remote.pressOnButton();    // Turning on the TV.remote.pressMuteButton();  // Unmuting the TV.return 0;
}