类和结构体中的Static

类/结构体中的static，表明这个符号在这个类的所有对象共用。不属于任何一个对象。调用时直接用命名空间来访问这个符号。（函数内的静态变量不做讨论，和C语言是一样的）

下面是一些例子：

没有使用static：

#include <iostream>

using namespace std;

class Player{
public:
    int x = 0, y = 0;
    void move(int xa, int ya){
        cout << "move from (" << x << "," << y << ") to \
(" << x+xa << "," << y+ya << ")" << endl;
        x += xa;
        y += ya;
    };
};

int main()
{
    Player player;
    player.move(2,7);
    player.move(3,5);
    return 0;
}

静态成员变量：

#include <iostream>

using namespace std;

class Player{
public:
    static int x, y;
    void move(int xa, int ya){
        cout << "move from (" << x << "," << y << ") to \
(" << x+xa << "," << y+ya << ")" << endl;
        x += xa;
        y += ya;
    };
};

int Player::x;
int Player::y;

int main()
{
    Player player1;
    Player player2;
    Player::x = 3;
    Player::y = 6;
    Player::y = 6;
    player1.move(2,7);
    player2.move(3,5);
    return 0;
}

静态成员方法：

• 注意，类中静态方法不能访问非静态成员。

#include <iostream>

using namespace std;

class Player{
public:
    int x = 0, y = 0;
    static void move(Player& player, int xa, int ya){
        cout << "move from (" << player.x << "," << player.y << ") to \
(" << player.x+xa << "," << player.y+ya << ")" << endl;
        player.x += xa;
        player.y += ya;
    };
};

int main()
{
    Player player;
    Player::move(player, 2, 7);
    Player::move(player, 3, 5);
    return 0;
}