1. 不好的代码

1.1 lib.cpp

class Library{
public:void Step1(){//...}void Step3(){//...}void Step5(){//...}
};

1.2 app.cpp

class Application{
public:bool Step2(){//...}void Step4(){//...}
};int main()
{Library lib();Application app();lib.Step1();if(app.Step2()){lib.Step3();}for(int i=0; i<4; i++){app.Step4();}lib.Step5();
}

1.3 概括

2. 好的代码

2.1 lib.cpp

class Library{
public://稳定 template methodvoid Run(){Step1();if(Step2()){	//支持变化 ==> 虚函数的多态调用Step3();}for(int i=0; i<4; i++){Step4();	//支持变化 ==> 虚函数的多态调用}Step5();}virtual ~Library(){ }protected:void Step1(){ //稳定//...}void Step3(){ //稳定//...}void Step5(){ //稳定//...}virtual bool Step2() = 0;	//变化virtual void Step4() = 0;	//变化};

2.2 app.cpp

class Application : public Library{
protected:virtual bool Step2(){//... 子类重写实现}virtual void Step4(){//... 子类重写实现}
};int main()
{Library* pLib = new Application();pLib->Run();delete pLib;
}

2.3 概括