C++ 方法线程

Question

我想为类中的方法创建一个线程。我写了这个:

class Program
{
    public:
        Program();
        void render();
};

Program::Program()
{
    thread t(render);
}

void Program::render()
{
    cout << "Hello" << endl;
}

这给了我这个错误信息:

“错误 C3867:‘Program::render’:函数调用缺少参数列表；使用‘&Program::render’创建指向成员的指针”

当我改为这样写时:

thread t(&Program::render);

它说:

1>c:\program files(x86)\microsoft visual studio 12.0\vc\include\functional(1149) : error C2064 : term does not evaluate to a function taking 0 arguments
1>          class does not define an 'operator()' or a user defined conversion operator to a pointer - to - function or reference - to - function that takes appropriate number of arguments
1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\functional(1137) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Program::* )(void),void,Program,>,>::_Do_call<,>(std::tuple<>,std::_Arg_idx<>)' being compiled
1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\functional(1137) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Program::* )(void),void,Program,>,>::_Do_call<,>(std::tuple<>,std::_Arg_idx<>)' being compiled
1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\thr\xthread(195) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Program::* )(void),void,Program,>,>::operator ()<>(void)' being compiled
1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\thr\xthread(195) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Program::* )(void),void,Program,>,>::operator ()<>(void)' being compiled
1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\thr\xthread(192) : while compiling class template member function 'unsigned int std::_LaunchPad<_Target>::_Run(std::_LaunchPad<_Target> *)'
1>          with
1>[
    1>              _Target = std::_Bind<true, void, std::_Pmf_wrap<void(__thiscall Program::*)(void), void, Program, >, >
        1>]
        1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\thr\xthread(187) : see reference to function template instantiation 'unsigned int std::_LaunchPad<_Target>::_Run(std::_LaunchPad<_Target> *)' being compiled
        1>          with
        1>[
            1>              _Target = std::_Bind<true, void, std::_Pmf_wrap<void(__thiscall Program::*)(void), void, Program, >, >
                1>]
                1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\thr\xthread(205) : see reference to class template instantiation 'std::_LaunchPad<_Target>' being compiled
                1>          with
                1>[
                    1>              _Target = std::_Bind<true, void, std::_Pmf_wrap<void(__thiscall Program::*)(void), void, Program, >, >
                        1>]
                        1>          c:\program files(x86)\microsoft visual studio 12.0\vc\include\thread(49) : see reference to function template instantiation 'void std::_Launch<std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Program::* )(void),void,Program,>,>>(_Thrd_t *,_Target &&)' being compiled
                        1>          with
                        1>[
                            1>              _Target = std::_Bind<true, void, std::_Pmf_wrap<void(__thiscall Program::*)(void), void, Program, >, >
                                1>]
                                1>          c:\users\erik\documents\visual studio 2013\projects\c++gameengine\c++gameengine\program.cpp(16) : see reference to function template instantiation 'std::thread::thread<void(__thiscall Program::* )(void),>(_Fn &&)' being compiled
                                1>          with
                                1>[
                                    1>              _Fn = void(__thiscall Program::*)(void)
                                        1>]

不太明白哪里不对。你能解释一下并给我一个解决方案吗？

Answer 1

render 是一个非静态成员函数，所以它需要一个对象来调用它。您需要将它包装在一个小函数对象中，以便在 Program 上调用它。根据口味，有两种方便的方法可以做到这一点:

thread t(&Program::render, this);
thread t([this]{render();});

下一个问题是线程是构造函数的本地线程，因此会立即被销毁。您不能在未加入(等待线程完成)或分离线程对象的情况下销毁线程对象。所以要么让它成为成员(member)，这样你以后就可以加入它；或在返回前将其分离。