class Timer {
	std::atomic<bool> active{true};
	
    public:
         
        void setInterval(auto function, int interval);
        void stop();
};
void Timer::setInterval(auto function, int interval) {
    active = true;
    std::thread t([=]() {
        while(active.load()) {
            std::this_thread::sleep_for(std::chrono::milliseconds(interval));
            if(!active.load()) return;
            function();
        }
    });
    t.detach();
}
void Timer::stop() {
    active = false;
}

int main()
{
    printf("start\n");
    Timer* timer = new Timer();
    timer->setInterval([&]() {
        std::cout << "hello" << std::endl;
    },1000); 
    return 0;
};

/usr/bin/g++ -fdiagnostics-color=always -std=c++14 -pthread -g /home/vagrant/cpp/batch/main.cpp -o /home/vagrant/cpp/batch/main

#include <atomic>
#include <thread>
#include <chrono>
#include <iostream>
class Timer {
private:
std::atomic<bool> active = false;
std::unique_ptr<std::thread> timer_thread;
public:
// this class needs a destructor.
~Timer()
{
stop();
}
// this function name is misleading, 
// void setInterval(auto function, int interval);
//
// let's rename it to what it does, also try to keep 
// the function argument last, this makes the code
// more legible when calling with a lambda.
//
// you do not know if 'cb', the caller's callable object
// is copyable or moveable, so you should use perfect 
// forwarding, that's only (readily) available from a 
// template.
template <typename Fn>
void start(int interval, Fn&& cb)
{
stop();  // make sure we're stopped.
active = true;
// start the thread, the forward<> of the callback object is 
// important!
timer_thread = std::make_unique<std::thread>(
[this, ms = std::chrono::milliseconds(interval), cb = std::forward<Fn>(cb)]() {
while (active) // calls atomic<>::load() automatically
{
std::this_thread::sleep_for(ms);
if (active)
cb();
}
});
}
// this is where we kill the thread, and wait for it to exit.
void stop()
{
active = false;
if (timer_thread)
{
timer_thread->join();
timer_thread.reset();
}
}
bool isRunning() const 
{
return active;
}
};
int main()
{
std::cout << "start\n";
Timer timer;  // There's absolutely no need to place timer on the heap.
int n = 4;    // simple countdown to 1 for example.
timer.start(1000, [&]() { 
std::cout << "countdown: " << n << '\n';
if (--n <= 0) 
timer.stop(); 
});
// We should wait for the timer to stop, before exiting the program.
while (timer.isRunning()) {}
return 0;
};