title: swift UNUserNotificationCenter with function
body: <p>I am using <code>UNUserNotificationCenter</code> for my app development.</p>
  
  <p>I would like to apply a function to the <code>UNUserNotificationCenter</code> just before the <code>UNUserNotificationCenter</code> is turned on and the data obtained from that function.</p>
  
  <p>I think it is inaccurate and inaccurate to compare the time I set for an alarm with a timer every fixed time.</p>
  
  <p>What method should be used to get a function to run at a certain time?</p>