是否可以定义std :: thread并稍后对其进行初始化？ [英] Is it possible to define an std::thread and initialize it later?

问题描述

我的目标是保留 std :: thread 对象作为数据成员，并在需要时对其进行初始化。

我无法这样做（如下面的代码所示）是因为 std :: thread 类的副本构造函数被删除了。还有其他方法吗？

My aim is to keep an std::thread object as data member, and initialize it when needed.
I'm not able to do this (as in my code below) because the copy constructor of the std::thread class is deleted. Is there any other way to do it?

class MyClass
{
    public:
        MyClass():DiskJobThread(){};
        ~MyClass();

        void DoDiskJobThread();

    private:
        int CopyThread(const std::wstring & Source, const std::wstring & Target);
        int MoveThread(const std::wstring & Source, const std::wstring & Target);
        std::thread DiskJobThread;
};

MyClass::~MyClass()
{
    DiskJobThread.join();
}

void MyClass::DoDiskJobThread()
{
    std::wstring Source = GetSource();
    std::wstring Target = GetTarget();
    int m_OperationType = GetOperationType();
    if      (m_OperationType == OPERATION_COPY)
    {
        DiskJobThread = std::thread(&MyClass::CopyThread, *this, Source, Target);
    }
    else if (m_OperationType == OPERATION_MOVE)
    {
        DiskJobThread = std::thread(&MyClass::MoveThread, *this, Source, Target);
    }
}

推荐答案

您的问题是另外一回事-您正在将 MyClass 的实例传递到线程中，而不是指向 MyClass 的指针。成员函数期望。只需像这样更改 DoDiskJobThread（）（不要取消引用 this ）：

Your problem is something else - you're passing an instance of MyClass into the thread instead of the pointer to MyClass which the member functions expect. Simply change DoDiskJobThread() like this (do not dereference this):

void MyClass::DoDiskJobThread()
{
    std::wstring Source = GetSource();
    std::wstring Target = GetTarget();
    int m_OperationType = GetOperationType();
    if      (m_OperationType == OPERATION_COPY)
    {
        DiskJobThread = std::thread(&MyClass::CopyThread, this, Source, Target);
    }
    else if (m_OperationType == OPERATION_MOVE)
    {
        DiskJobThread = std::thread(&MyClass::MoveThread, this, Source, Target);
    }
}

由于 *此导致尝试将 MyClass 复制到线程函数中，并且类的副本ctor被删除（因为 std :: thread 被删除）。但是，成员函数 CopyThread 和 MoveThread 仍然需要一个指针作为第一个（隐藏的）参数。

You were getting the error because *this resulted in trying to copy MyClass into the thread function, and the copy ctor of your class is deleted (because that of std::thread is deleted). However, the member functions CopyThread and MoveThread require a pointer as the first (hidden) argument anyway.

现场演示

Live demonstration

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