将std :: thread对象存储为类成员 [英] Storing an std::thread object as a class member

问题描述

我想在类中保留 std :: thread 对象。

  class GenericWindow 
 {
 public：
 void Create（）
 {
 // ... 
 MessageLoopThread = std :: thread（& GenericWindow :: MessageLoop，* this）; 
} 
 private：
 std :: thread MessageLoopThread; 
 void GenericWindow :: Destroy（）//从析构函数调用
 {
 SendMessageW（m_hWnd，WM_DESTROY，NULL，NULL）; 
 UnregisterClassW（m_ClassName.c_str（），m_WindowClass.hInstance）; 
 MessageLoopThread.join（）; 
} 
 void GenericWindow :: MessageLoop（）
 {
 MSG Msg; 
 while（GetMessageW（& Msg，NULL，0，0））
 {
 if（！IsDialogMessageW（m_hWnd，& Msg））
 {
 TranslateMessage （& Msg）; 
 DispatchMessageW（& Msg）; 
} 
} 
} 
}; // LINE 66 
  

错误：

 [Line 66]错误C2248：'std :: thread :: thread'：无法访问在'std :: thread'类中声明的私有成员

这个错误信息不帮助我，我不是试图访问 std :: thread 类的任何私人成员。

我的代码有什么问题？

$ p

<$ p

解决方案

$ p> MessageLoopThread = std :: thread（& GenericWindow :: MessageLoop，* this）;


您将 * this std :: thread 构造函数，它将尝试使副本传递到新生成的线程。 * this 当然是不可复制的，因为它有一个 std :: thread 成员。如果您要传递参考，则需要将其放在 std :: reference_wrapper ：

  MessageLoopThread = std :: thread（& GenericWindow :: MessageLoop，
 std :: ref（* this））; 
  

I'm trying to keep an std::thread object inside a class.

class GenericWindow
{
    public:
        void Create()
        {
            // ...
            MessageLoopThread = std::thread(&GenericWindow::MessageLoop, *this);
        }
    private:
        std::thread MessageLoopThread;
        void GenericWindow::Destroy()   // Called from the destructor
        {
            SendMessageW(m_hWnd, WM_DESTROY, NULL, NULL);
            UnregisterClassW(m_ClassName.c_str(), m_WindowClass.hInstance);
            MessageLoopThread.join();
        } 
        void GenericWindow::MessageLoop()
        {
            MSG Msg;
            while (GetMessageW(&Msg, NULL, 0, 0))
            {
                if (!IsDialogMessageW(m_hWnd, &Msg))
                {
                    TranslateMessage(&Msg);
                    DispatchMessageW(&Msg);
                }
            }
        }
};      // LINE 66

Error given:

[Line 66] Error C2248: 'std::thread::thread' : cannot access private member declared in class 'std::thread'

This error message doesn't help me, I'm not trying to access any private member of the std::thread class.

What is wrong in my code? How do I fix it?

解决方案

On this line:

MessageLoopThread = std::thread(&GenericWindow::MessageLoop, *this);

You are passing *this by value to the std::thread constructor, which will try to make a copy to pass to the newly spawned thread. *this is of course noncopyable, since it has a std::thread member. If you want to pass a reference, you need to put it in a std::reference_wrapper:

MessageLoopThread = std::thread(&GenericWindow::MessageLoop,
                                std::ref(*this));

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