引入：小菜一天的工作状态，上午状态好，效率高。中午犯困想睡觉，下午逐渐恢复精神，开始疯狂赶进度。 这就是状态跟随时间的变化。
一、工作状态变化-函数版
main.cpp
#includeusing namespace std; static int Hour = 0; // 时间 static bool WorkFinished = false; // 任务完成标记 static void WriteProgrtam() { if (Hour < 12 && Hour >= 8) { cout << "当前时间: " << Hour << ",上午工作，精神百倍。" << endl; } else if (Hour >= 12 && Hour < 13) { cout << "当前时间: " << Hour << ",又饿又困，需要午休。" << endl; } else if (Hour >= 13 && Hour < 17) { cout << "当前时间: " << Hour << ",下午状态不错，继续努力。" << endl; } else { if (WorkFinished) { cout << "当前时间: " << Hour << ", 任务完成，下班回家！" << endl; } else { if (Hour < 21) { cout << "当前时间: " << Hour << ",加班吧，疲劳至极。" << endl; } else { cout << "当前时间: " << Hour << ",不行了，睡觉。" << endl; } } } } int main() { Hour = 9; WriteProgrtam(); Hour = 10; WriteProgrtam(); Hour = 11; WriteProgrtam(); Hour = 12; WriteProgrtam(); Hour = 13; WriteProgrtam(); Hour = 14; WriteProgrtam(); Hour = 17; WriteProgrtam(); WorkFinished = true; WriteProgrtam(); WorkFinished = false; Hour = 19; WriteProgrtam(); Hour = 22; WriteProgrtam(); system("pause"); return 0; }
运行结果：
很粗糙的实现，根本不是面向对象编程的思想。
二、工作状态-分类版
设置一个工作类，其中Hour以及workFinished是该类的属性。writePrograme是该类的一个方法。
Work.h
#pragma once #includeusing namespace std; class Work { private: int Hour = 0; bool WorkFinished = false; public: void writeProgram(); void setHour(int Hour); int getHour(); void setWorkFinished(bool WorkFinished); bool getWorkFinished(); };
Work.cpp
#include "Work.h"
void Work::writeProgram()
{
if (this->Hour < 12 && this->Hour >= 8)
{
cout << "当前时间: " << this->Hour << ",上午工作，精神百倍。" << endl;
}
else if (this->Hour >= 12 && this->Hour < 13)
{
cout << "当前时间: " << this->Hour << ",又饿又困，需要午休。" << endl;
}
else if (this->Hour >= 13 && this->Hour < 17)
{
cout << "当前时间: " << this->Hour << ",下午状态不错，继续努力。" << endl;
}
else
{
if (WorkFinished)
{
cout << "当前时间: " << this->Hour << ", 任务完成，下班回家！" << endl;
}
else
{
if (this->Hour < 21)
{
cout << "当前时间: " << this->Hour << ",加班吧，疲劳至极。" << endl;
}
else
{
cout << "当前时间: " << this->Hour << ",不行了，睡觉。" << endl;
}
}
}
}
void Work::setHour(int Hour)
{
this->Hour = Hour;
}
int Work::getHour()
{
return this->Hour;
}
void Work::setWorkFinished(bool WorkFinished)
{
this->WorkFinished = WorkFinished;
}
bool Work::getWorkFinished()
{
return this->WorkFinished;
}
客户端：
#include#include"Work.h" void test01() { // emergency project Work* emergencyProjects = new Work(); emergencyProjects->setHour(9); emergencyProjects->writeProgram(); emergencyProjects->setHour(10); emergencyProjects->writeProgram(); emergencyProjects->setHour(12); emergencyProjects->writeProgram(); emergencyProjects->setHour(13); emergencyProjects->writeProgram(); emergencyProjects->setHour(14); emergencyProjects->writeProgram(); emergencyProjects->setHour(17); emergencyProjects->writeProgram(); emergencyProjects->setWorkFinished(false); emergencyProjects->writeProgram(); emergencyProjects->setHour(19); emergencyProjects->writeProgram(); emergencyProjects->setHour(22); emergencyProjects->writeProgram(); cout << "-------------------------------" << endl; cout << endl; emergencyProjects->setWorkFinished(true); emergencyProjects->setHour(17); emergencyProjects->writeProgram(); emergencyProjects->setHour(19); emergencyProjects->writeProgram(); emergencyProjects->setHour(22); emergencyProjects->writeProgram(); emergencyProjects = NULL; delete emergencyProjects; } int main() { test01(); system("pause"); return 0; }
运行结果：
存在的问题：
Work类的writeProgram()方法是一个“Long Method”，也就是说这个方法过长。
同时该方法内保护大量的if-else判断分支，意味着它的责任过大。
而面向对象设计希望做到代码责任分解，即做到“单一职责原则”。
目前的writeProgram()如果需要修改，修改代价、难度大。
三、状态模式（State Pattern）
状态模式（State）,当一个对象的内在状态改变时允许改变其行为，这个对象看起来像是改变其类。
本质：解决当控制一个对象状态转换的条件表达式过于复杂时的情况。把状态的判断逻辑转移到表示不同状态的一系列类当中，可以把复杂的判断逻辑简化。
状态模式的有点：将于特定状态相关的行为局部化，并且将不同状态的行为分割开来。
使用状态模式的时机：如果某个对象的行为取决于它的状态，并且它必须在运行时刻根据状态改变它自身的行为，就可以考虑使用状态模式。
四、工作状态-状态模式版
State.h 抽象状态类
#pragma once #include#include"Work.h" using namespace std; // 抽象状态类 class State { public: virtual void WriteProgram(Work* w) = 0; };
Work.h
#pragma once #include// #include"State.h" // #include"ForenoonState.h" using namespace std; class State; class Work { private: State* current; double hour; bool finish = false; public: Work(); void setHour(double hour); double getHour(); void setWorkFinished(bool finish); bool getWorkFinished(); void setState(State* s); void WriteProgram(); };
Work.cpp
#include "Work.h"
#include "ForenoonState.h"
Work::Work()
{
// 初始化状态为上午工作状态
current = new ForenoonState;
}
void Work::setHour(double hour)
{
this->hour = hour;
}
double Work::getHour()
{
return this->hour;
}
void Work::setWorkFinished(bool finish)
{
this->finish = finish;
}
bool Work::getWorkFinished()
{
return this->finish;
}
void Work::setState(State* s)
{
current = s;
}
void Work::WriteProgram()
{
current->WriteProgram(this);
}
【Mark】问题记录：
在编译项目时遇到了 error C2504： “State” 未定义基类的问题
针对这个问题，我参考了这篇博客，启发很大：
error C2504: 未定义基类_wklnewlife的博客-CSDN博客_c++ 未定义基类
原因就是我在main文件中头文件的编译顺序是首先编译State.h，State.h中由要引入Work.h，然而Work.h中又包含了State.h的头文件。因此变成了一个闭环。导致无法编译而报错。
此外，我Work.h中需要使用ForenoonState类来初始化我的Work构造函数。但是，ForenoonStatge.h还是需要引入State.h文件，怎么办？
在Work.cpp文件中引入ForenoonState.h即可。
ForenoonState.h 上午工作状态类
#pragma once #include#include"State.h" #include #include"NoonState.h" using namespace std; class ForenoonState : public State { public: void WriteProgram(Work* w); };
ForenoonState.cpp
#include "ForenoonState.h"
void ForenoonState::WriteProgram(Work* w)
{
if (w->getHour() < 12)
{
cout << "当前时间：" + to_string(w->getHour()) << "点,上午工作，精神百倍！" << endl;
}
else
{
w->setState(new NoonState);
w->WriteProgram();
}
}
NoonState.h 中午工作状态类
#pragma once #include#include #include"State.h" #include"ForenoonState.h" #include"AfternoonState.h" using namespace std; class NoonState : public State { public: void WriteProgram(Work* w); };
NoonState.cpp
#include "NoonState.h"
void NoonState::WriteProgram(Work* w)
{
if (w->getHour() < 13)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，饿了，吃午饭；犯困，午休。" << endl;
}
else
{
w->setState(new AfternoonState);
w->WriteProgram();
}
}
AternoonState.h 下午工作状态类
#pragma once #include#include #include"State.h" #include"EveningState.h" using namespace std; class AfternoonState : public State { public: void WriteProgram(Work* w); };
AternoonState.cpp
#include "AfternoonState.h"
void AfternoonState::WriteProgram(Work* w)
{
if (w->getHour() < 17)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，下午状态还不错，继续努力。" << endl;
}
else
{
w->setState(new EveningState);
w->WriteProgram();
}
}
EveningState.h 晚上的工作状态类
#pragma once #include#include #include"State.h" #include"SleepingState.h" #include"RestState.h" using namespace std; class EveningState :public State { public: void WriteProgram(Work* w); };
EveningState.cpp
#include "EveningState.h"
void EveningState::WriteProgram(Work* w)
{
if (w->getWorkFinished())
{
w->setState(new RestState);
w->WriteProgram();
}
else
{
if (w->getHour() < 21)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，加班哦，疲累至极。" << endl;
}
else
{
w->setState(new SleepingState);
w->WriteProgram();
}
}
}
RestState.h 休息状态类
#pragma once #include#include #include"State.h" using namespace std; class RestState : public State { public: void WriteProgram(Work* w); };
RestState.cpp
#include "RestState.h"
void RestState::WriteProgram(Work* w)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，下班回家了。" << endl;
}
SleepingState.h 睡觉状态类
#pragma once #include#include #include"State.h" using namespace std; class SleepingState : public State { public: void WriteProgram(Work* w); };
SleepingState.cpp
#include "SleepingState.h"
void SleepingState::WriteProgram(Work* w)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，不行了，睡着了。" << endl;
}
客户端（完全一样）：
#pragma once #include#include"State.h" #include"ForenoonState.h" #include"NoonState.h" #include"AfternoonState.h" #include"EveningState.h" #include"SleepingState.h" #include"RestState.h" void test01() { Work* emergencyProjects = new Work(); emergencyProjects->setHour(9); emergencyProjects->WriteProgram(); emergencyProjects->setHour(10); emergencyProjects->WriteProgram(); emergencyProjects->setHour(12); emergencyProjects->WriteProgram(); emergencyProjects->setHour(13); emergencyProjects->WriteProgram(); emergencyProjects->setHour(14); emergencyProjects->WriteProgram(); emergencyProjects->setHour(17); emergencyProjects->WriteProgram(); emergencyProjects->setWorkFinished(true); emergencyProjects->WriteProgram(); emergencyProjects->setHour(19); emergencyProjects->WriteProgram(); emergencyProjects->setHour(22); emergencyProjects->WriteProgram(); cout << endl; cout << "---------------------" << endl; cout << endl; emergencyProjects->setWorkFinished(false); emergencyProjects->WriteProgram(); emergencyProjects->setHour(19); emergencyProjects->WriteProgram(); emergencyProjects->setHour(22); emergencyProjects->WriteProgram(); emergencyProjects = NULL; delete emergencyProjects; } int main() { test01(); system("pause"); return 0; }
运行结果：
现在，增加一个需求，老板要求20点之后必须回家。
在状态模式下很好修改，增加一个ForceToLeave状态类，同样继承自State这个抽象状态。
ForceToLerave.h
#pragma once #include#include #include"State.h" class ForceToLeave : public State { public: void WriteProgram(Work* w); };
ForceToLerave.cpp
#include "ForceToLeaveState.h"
void ForceToLeave::WriteProgram(Work * w)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，不许内卷，赶快回家！" << endl;
}
在晚上工作状态类进行逻辑修改：
#include "EveningState.h"
void EveningState::WriteProgram(Work* w)
{
if (w->getWorkFinished())
{
w->setState(new RestState);
w->WriteProgram();
}
else
{
if (w->getHour() < 20 && w->getHour() >= 17)
{
cout << "当前时间：" + to_string(w->getHour()) << "点，加班哦，疲累至极。" << endl;
}
else if (w->getHour() >= 20 && w->getHour() < 22)
{
w->setState(new ForceToLeave);
w->WriteProgram();
}
else
{
w->setState(new SleepingState);
w->WriteProgram();
}
}
}
运行结果：
参考资料：《大话设计模式》，作者：程杰
