请设计4个类，“上帝”，“动物”，“狗”，“牛”，请简要写出类定义和实现代码，如有必要，可以引入辅助类。
1、全世界只有一个“上帝”。
2、只有“上帝”才能创造“动物”，“上帝”根据“动物”的名字创造“动物”。
3、所有的“动物”都会跑。
4、“狗”会吠。
5、“牛”会吃。
#include <iostream>
#include <string>
using namespace std;
class Animal
{
public:
void run()
{
cout << "runing." << endl;
}
virtual void DoSomething()
{
cout << "do something." << endl;
}
virtual ~Animal()
{
}
};
class Dog:public Animal
{
public:
void DoSomething()
{
cout << "dog bark." << endl;
}
};
class Cow:public Animal
{
public:
void DoSomething()
{
cout << "cow eat." << endl;
}
};
class God
{
public:
static God* CreatInstance();
Animal* CreateAnimal(string animalName)
{
if (animalName == "Dog")
{
pAnimal = new Dog();
}
else if (animalName == "Cow")
{
pAnimal = new Cow();
}
else
{
pAnimal = new Animal();
}
return pAnimal;
}
~God()
{
delete instance;
delete pAnimal;
}
private:
static God* instance;
Animal* pAnimal;
string animaName;
God()
: animaName("")
, pAnimal(NULL)
{
}
};
God* God::instance = NULL;
God* God::CreatInstance()
{
if (instance == NULL)
{
instance = new God();
}
return instance;
}
int _tmain(int argc, _TCHAR* argv[])
{
God * pGod = God::CreatInstance(); // There is only one god
Animal* pAnimal = NULL;
pAnimal = pGod->CreateAnimal("Dog"); // God Creat Dog.
pAnimal->run();
pAnimal->DoSomething();
pAnimal = pGod->CreateAnimal("Cow"); // God Creat Cow.
pAnimal->run();
pAnimal->DoSomething();
int pause = 0;
cin >> pause;
return 0;
}
