Decorator for a class method

Question

Supposing I have a function (a decorator) that measures the duration of given function:

#include 

void measure(void (*f)()) {
    time_t tBe         


        

Answer 1

1. Change measure to a function template to allow you to use any callable, not just a function.

2. Use a lambda function in run.

---

#include 
#include 
#include 

template 
void measure(F f) {
    time_t tBegin = time(NULL);
    f();
    time_t tEnd = time(NULL);
    std::cout << "Duration: " << (tEnd - tBegin) << " sec" << std::endl;
}

class Myclass {
private:
    double _d;

public:
    Myclass(double d) : _d(d) {}

    void run() {
        measure([=](){m();});
    }

    void m() const {
        usleep(1000000 * _d);
    }
};

int main() {
    Myclass obj(2.0);
    obj.run();
    return 0;
}

---

Since, you are not allowed to modify measure, you can use a helper class template and a function template to make it possible for you to use any callable.

#include 
#include 
#include 

void measure(void (*f)()) {
    time_t tBegin = time(NULL);
    f();
    time_t tEnd = time(NULL);
    std::cout << "Duration: " << (tEnd - tBegin) << " sec" << std::endl;
}

template 
struct MeasureFunctor
{
   static F* f_;
   static void run(){(*f_)();}
};

template  F* MeasureFunctor::f_ = nullptr;

template 
void measure(F f) {
   MeasureFunctor::f_ = &f;
   measure(MeasureFunctor::run);
}

class Myclass {
private:
    double _d;

public:
    Myclass(double d) : _d(d) {}

    void run() {
        measure([=](){m();});
    }

    void m() const {
        usleep(1000000 * _d);
    }
};

int main() {
    Myclass obj(2.0);
    obj.run();
    return 0;
}