具有可变参数的函数作为函数 C++ 的参数

Question

I am trying to create measuring class with one function that take function to be measured as parameter. Its called ChronoTimer.h content is:

#include <chrono>

template<typename TimeT = std::chrono::milliseconds, class ClockT = 
std::chrono::system_clock>

class ChronoTimer {
public:
    template<typename F, typename ...Args>

    static typename TimeT::rep duration(F func, Args&&... args)
    {
        auto start = ClockT::now();
        func(std::forward<Args>(args)...);
        return  std::chrono::duration_cast<TimeT>(ClockT::now() - start);
    }
};

Then I have "someClass" where is a function i want measure, and a function where I want to measure the function

#include "ChronoTimer.h"
long int someClass::measuredF( long end ) {
    long int cnt = 0;
    for ( long int i = 0; i < end; ++i ) {
        cnt = cnt + i;
    }
    return cnt;
}

void someClass::someFunction() {
    long int end = 10;
    auto duration = ChronoTimer<>::duration(someClass::*measuredF, end).count();
}

There is an error and i dont have enough understing/knowledge in C++ to get it working. Appreciate any help, thanks

Answer 1

You should pass a callable object, &someClass::measuredF is not callable, its requires a someClass object.

You may do:

void someClass::someFunction() {
    long int end = 10;
    auto duration = ChronoTimer<>::duration([this](long int end) { this->measuredF(end); }, end).count();
}

or capture all:

void someClass::someFunction() {
    long int end = 10;
    auto duration = ChronoTimer<>::duration([=]() { this->measuredF(end); }).count();
}