ubtuntu+cmake+c++

单例模式与工厂函数

#include <iostream>
#include <list>
#include <functional>

// 前向声明
void *create_board();

// Board基类（抽象类，不可直接实例化）
class Board
{
protected:
    Board() {} // 允许派生类构造
public:
    static Board &GetInstance()
    {
        static Board *instance = static_cast<Board *>(create_board());
        return *instance;
    }
    virtual void ShowInfo() = 0; // 纯虚函数，强制派生类实现
    virtual ~Board() = default;
};

// 派生类
class MyBoard : public Board
{
public:
    void ShowInfo() override
    { // 实现纯虚函数
        std::cout << "This is MyBoard\n";
    }
};

// 宏生成工厂函数
#define DECLARE_BOARD(BOARD_CLASS_NAME) \
    void *create_board() { return new BOARD_CLASS_NAME(); }

DECLARE_BOARD(MyBoard); // 生成 create_board() 返回 new MyBoard()

int main()
{
    Board &board = Board::GetInstance();
    board.ShowInfo(); // 输出 "This is MyBoard"
    return 0;
}