C++ 在基类中使用已删除函数 std::unique_ptr

Question

我有一个 vector 或游戏对象。我必须为 C++11 编译

std::vector< std::unique_ptr<Game> > games_;

Game是基类，这样定义

class Game {

public:

        Game(int id, const std::string& name)
                : id_(id), name_(name){}

        virtual ~Game(); 

        int play(int w);
        virtual void validate() = 0;

        int id_;
        std::string name_;

};

派生类只是实现了 validate() 方法。

现在我的经理类想要将“玩游戏”发布到线程池。这样做:

void Manager::playGames() {


        boost::asio::io_service ioService;

        std::unique_ptr<boost::asio::io_service::work> work( new boost::asio::io_service::work(ioService));

        boost::thread_group threadpool; //pool
        std::cout << "will start for " << playthreads_ << " threads and " << getTotalRequests() << "total requests\n";
        for (std::size_t i = 0; i < playthreads_; ++i)
                threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioService));

        for ( std::size_t i=0; i < w_.size(); i++) {

                ioService.post(boost::bind(&Game::play, games_[i], 2));

        }    

        work.reset();
        threadpool.join_all();
        ioService.stop();

}

错误是

/home/manager.cpp: In member function ‘void Manager::playGames()’:
/home//manager.cpp:65:74: error: use of deleted function
 ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&)
 [with _Tp = Game; _Dp = std::default_delete<Game>]’ 
 ioService.post(boost::bind(&Game::play, games_[i], 2));
                                                                          ^
In file included from /opt/5.2/include/c++/5.2.0/memory:81:0,
                 from /home/manager.hpp:5,
                 from /home/manager.cpp:1: /opt/5.2/include/c++/5.2.0/bits/unique_ptr.h:356:7: note: declared
here
       unique_ptr(const unique_ptr&) = delete;

Answer 1

对于 boost::bind(&Game::play, games_[i], 2)，games_[i] 被复制到绑定(bind)，但是 std::unique_ptr 无法复制。 (只能移动，但我觉得移动到这里不符合要求。)

您可以使用 boost::ref 来避免复制，例如

ioService.post(boost::bind(&Game::play, boost::ref(games_[i]), 2));