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Bellow 是示例代码，它演示了我正在尝试做的事情。

基本上，我想将多个指向成员的指针传递给类方法，该类方法接受std::function传递给目标函数对象的对象和变量号或参数。

这些变量参数可以是任何东西：变量、指向成员的指针等。

使用普通变量时我没有问题，但是如何扩展参数包，其中参数是指向成员的指针，但函数对象需要 POD 数据类型？

如何获取参数包中成员的指针值并将其传递给函数对象？

#include <cstddef>
#include <functional>


class Test
{
public:
    inline Test(std::uint32_t max);

    template<typename ReturnType, typename... Args>
    using Algorithm = std::function<ReturnType(Args...)>;

    // pointer to member
    // not used but would like to make use of it in 'RunTargetAlgo'
    template<typename T>
    using ParamType = T Test::*;

    // exectutor
    template<typename ReturnType, typename... Args, typename... Params>
    inline double RunTargetAlgo(Algorithm<ReturnType, Args...> target, Params... params);

    std::uint32_t mLoop = 0;
    const std::size_t mLoopMax;
    double mPrecision = 0;
};

Test::Test(std::uint32_t max) :
    mLoopMax(max)
{
}

template<typename ReturnType, typename ...Args, typename ...Params>
double Test::RunTargetAlgo(Algorithm<ReturnType, Args...> target, Params ...params)
{
    while (++mLoop <= mLoopMax)
        mPrecision += target(params...);    // How if Params == Test::ParamType ??

    // ... in real code we measure bunch of other stuff here...

    return mPrecision;
}

template<typename RetrunType>
RetrunType TestAlgorithm(std::uint32_t x, std::uint32_t y)
{
    // ...
    return RetrunType();
}

int main()
{
    namespace pl = std::placeholders;

    Test::Algorithm<double, std::uint32_t, std::uint32_t> algo =
        std::bind(TestAlgorithm<double>, pl::_1, pl::_2);

    Test t(50);

    // this works just fine!
    t.RunTargetAlgo(algo, 3u, 4u);

    // but how to run this?
    // I need pass fresh data to target algorithm, value of
    // pointer to members may change anytime.
    // but main issue here is how to extract these pointer from
    // parameter pack into actual values, but inside Test::RunTargetAlgo?
    t.RunTargetAlgo(algo, &Test::mLoop, &Test::mLoopMax);

    return 0;
}
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1 回答 1

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正如评论中所讨论的，假设您将所有参数都需要相同的操作，您可以简单地在参数包扩展中应用任何取消引用/成员访问操作。例如对于应该访问this实例的成员指针：

target(this->*params...);

或者如果您直接传递对象指针（这对我来说似乎更直接）：

target(*params...);

//...

t.RunTargetAlgo(algo, &t.mLoop, &t.mLoopMax);
于 2020-01-11T18:02:23.003 回答