Handling time in C++ - c++

Question

I am writing a simulation program. I have some difficulties when handling the time.
My program has a time period and a total elapsed time variables. I have traffic light objects. I want to change the color of them when the elapsed time is integer multiple of the period. For example, say total time starts from 0 and finishes in 60 seconds and the period is 10 seconds. So, when time is 10, 20, 30, etc. , the color should be changed.
I tried solving this issue with using simple math but nothing has been changed when I draw the objects. So, how can I handle the time to change their colors?

Answer 1

You can use the standard <chrono> library, but SFML has its own set of tools for handling time. You don't need any complicated calculations or threads. A simplified example of part of what you need:
#include <SFML/Graphics.hpp>
#include <vector>
class Light : public sf::CircleShape {
public:
Light(std::vector<sf::Color> cols, sf::Time period)
:colors{ cols }, colorIdx{ 0 }, changePeriod{ period }
{
setRadius(100);
}
void update(sf::Time deltaTime) {
elapsedTime += deltaTime;
while (elapsedTime >= changePeriod) {
elapsedTime -= changePeriod;
changeColor();
}
setColor();
}
protected:
void changeColor() {
if (++colorIdx == colors.size()) {
colorIdx = 0;
}
}
void setColor() {
setFillColor(colors[colorIdx]);
}
private:
std::vector<sf::Color> colors;
std::size_t colorIdx;
sf::Time changePeriod;
sf::Time elapsedTime;
};
int main() {
Light light1({sf::Color::Red, sf::Color::Yellow, sf::Color::Green}, sf::seconds(1));
Light light2({sf::Color::Red, sf::Color::Green}, sf::milliseconds(200));
light2.setPosition(300, 300);
light2.setRadius(20);
sf::RenderWindow window(sf::VideoMode(400, 400), "");
sf::Event event;
sf::Clock clock;
while (window.isOpen()) {
while (window.pollEvent(event)) {
if (event.type == sf::Event::Closed) window.close();
}
sf::Time dt = clock.restart();
light1.update(dt);
light2.update(dt);
window.clear();
window.draw(light1);
window.draw(light2);
window.display();
}
}

Answer 2

You could use delay(milliseconds) with the header file #include<dos.h>. For example if you want your traffic lights to be changed every 10 seconds in 60 seconds you could do the following code:
for(int i = 0; i < 6; i ++)
{
changeColor();
delay(1000);
}
Also, you could use sleep(). You may find the answer to your question here:
http://www.cplusplus.com/forum/beginner/13906/