c++第七章-（静态属性和静态方法）

class Pet
{
public:
    Pet(std::string theName);
    ~Pet();
    
    static int getCount();//公开的静态方法
protected:
    std::string name;
    
private:
    static int count;//私有的静态变量
};

class Dog:public Pet
{
public:
    Dog(std::string theName);
};

class Cat:public Pet
{
public:
    Cat(std::string theName);
};

int Pet::count = 0;//初始化静态变量

Pet::Pet(std::string theName)
{
    name = theName;
    count++;
    std::cout << "一只宠物出生了，名字叫做：" << name << std::endl;
}

Pet::~Pet()
{
    count--;
    std::cout << name << "挂掉了\n";
}

int Pet::getCount()
{
    return count;
}

Dog::Dog(std::string theName):Pet(theName)
{
    
}
Cat::Cat(std::string theName):Pet(theName)
{
    
}
int main(int argc, const char * argv[])
{
    Dog dog("Tom");
    Cat cat("Jerry");
    
    std::cout << "\n已经诞生了" << Pet::getCount() << "只宠物！\n\n" ;
    
    {//作用域的作用
        Dog dog2("Tom_2");
        Cat cat2("Jerry_2");
        
        std::cout << "\n现在呢，已经诞生了" << Pet::getCount() << "只宠物！\n\n" ;
    }

    std::cout << "\n现在还剩下 "
    << Pet::getCount()
    << " 只宠物!\n\n";
    
    return 0;
}

一只宠物出生了，名字叫做：Tom
一只宠物出生了，名字叫做：Jerry

已经诞生了2只宠物！

一只宠物出生了，名字叫做：Tom_2
一只宠物出生了，名字叫做：Jerry_2

现在呢，已经诞生了4只宠物！


现在还剩下 4 只宠物!

Jerry_2挂掉了
Tom_2挂掉了
Jerry挂掉了
Tom挂掉了

class Point
{
public:
    Point(int a,int b)
    {
        this->x = a;
        this->y = b;
    }
    ~Point()
    {
        std::cout << "this  = " << this << std::endl;//打印this地址
    }
    void MovePoint(int a,int b)
    {
        this->x = a;
        this->y = b;
    }
    void print()
    {
        std::cout << "x="
        << this->x
        << "\ny="
        << this->y << std::endl;
    }
private:
    int x,y;
};

int main(int argc, const char * argv[])
{
    Point point(10,10);
    std::cout << "point = " << &point << std::endl;//验证this指针与point是否同一个地址
    point.MovePoint(2, 2);//其实传到时候是以MovePoint(&point,2, 2);的形式传过去，只不过是将第一个参数隐藏了
    point.print();
 
    return 0;
}

point = 0x7fff5fbff8b8
x=2
y=2
this  = 0x7fff5fbff8b8