4elist1210.cpp

《21天学通C＋＋》附盘的原代码。书上的每个例子在这里都有相应的C语言程序。

//Listing 12.10 Data slistd:std::cing with passing by value

#include <iostream>

class Mammal
{
public:
	Mammal():itsAge(1) {  }
	virtual ~Mammal() { }
	virtual void Speak() const { std::cout << "Mammal speak!\n"; }
protected:
	int itsAge;
};

class Dog : public Mammal
{
public:
	void Speak()const { std::cout << "Woof!\n"; }
};

class Cat : public Mammal
{
public:
	void Speak()const { std::cout << "Meow!\n"; }
};

void ValueFunction (Mammal);
void PtrFunction   (Mammal*);
void RefFunction (Mammal&);
int main()
{
	Mammal* ptr=0;
	int choice;
	while (1)
	{
		bool fQuit = false;
		std::cout << "(1)dog (2)cat (0)Quit: ";
		std::cin >> choice;
		switch (choice)
		{
		case 0: fQuit = true;
				break;
		case 1: ptr = new Dog;
				break;
		case 2: ptr = new Cat;
				break;
		default: ptr = new Mammal;
				break;
		}
		if (fQuit)
			break;
		PtrFunction(ptr);
		RefFunction(*ptr);
		ValueFunction(*ptr);
	}
	return 0;
}

void ValueFunction (Mammal MammalValue)
{
	MammalValue.Speak();
}

void PtrFunction (Mammal * pMammal)
{
	pMammal->Speak();
}

void RefFunction (Mammal & rMammal)
{
	rMammal.Speak();
}