我不能让我的 function 计算已经过去了多少时间并相应地打印东西

Question

bool IsGameEnded()
{
    static int i = 0;

    i++;
    if (i == 10)
        return true;
    return false;
}

int main()
{

   bool GameEnd = false;
   
   float ElapsedTime = 0;
   while(!GameEnd)
   {
       chrono::steady_clock::time_point StartingTime = chrono::steady_clock::now();

       

       if (ElapsedTime > 10)
       {
           ElapsedTime = 0;
           draw();
       }

       GameEnd = IsGameEnded();
      
       chrono::steady_clock::time_point EndingTime = chrono::steady_clock::now();
       ElapsedTime = ElapsedTime + chrono::duration_cast<chrono::milliseconds>(EndingTime - StartingTime).count();
   }

   return 0;
}

I wan't to make a snake game. It will be based on time. For example screen will update every 5 seconds or so. For that I used chrono library. I am not used to this trying o learn it so I might have missed something obvious. But the problem is main function doesn't get get into the if block. So it draws nothing to the console.

I tried debugging (with running line by line). It is not actually like a running program becasue time intervals get long but it enters if block every time. Also if I make the if condition 2 nanoseconds it also works but since cout function can not print so fast I need it to be a lot longer than that. While Debugging I also realised that "StartingTime" and "EndingTime" variables don't get initiated (unless I directly stop on them). The interesting part is If ı add cout after if block, after a while program starts entering the If block.

Answer 1

When you do:

chrono::duration_cast<chrono::milliseconds>(EndingTime - StartingTime).count();

not enough time has passed, and the count of milliseconds always returns 0. This means you always add 0 to ElapsedTime and it never crosses 10.

One fix is to use a smaller resolution:

chrono::duration_cast<chrono::nanoseconds>(EndingTime - StartingTime).count();

as you mentioned in the question, and adjust the if condition appropriately.

However, the best fix would be to change ElapsedTime from a float to a chrono::duration (of the appropriate unit) since that is the unit that the variable represents. This would let you avoid having to do .count() on the duration as well.