Question

I’m testing a few things for my self in OS X, and I would like to know what the best way to do this would be.

I have a method, that returns the current week number.

-(NSInteger) getWeekNumber {
  NSDate *date = [NSDate date];
  NSCalendar *calendar = [NSCalendar currentCalendar];
  NSDateComponents *components = [calendar components:NSWeekCalendarUnit fromDate:date];

  return [components week];
}

Since this will only happen once a week it seems stupid to have a thread that will refresh my label once every second or so, but I want the label value to change at the exact second the week number change.

I also want to update a label with the current time, that will actually be once a second, or once a minute depending on settings. Should that just be a thread that runs once a second?

Answer 1

There is no need to use threads for simple tasks like these.
NSTimer is the way to go, do something like this for the weekly updates:

// Exact moment the new week starts
NSDate *date = 

// Imagine the new week starts in 5 seconds
NSDate *date = [NSDate dateWithTimeIntervalSinceNow:5]; 

NSTimer *timer = [[NSTimer alloc]
                  initWithFireDate: date
                  interval: 60*60*24*7 // Equals one week
                  target: self
                  selector: @selector(updateWeekLabel:)
                  userInfo: nil
                  repeats: NO
                  ];

[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];

The following function will be triggered when the new week starts:

-(void)updateWeekLabel:(NSTimer*)theTimer
{
    // Get current week and update the label.
    // Wait for next week or invalidate the timer like this:
    [theTimer invalidate];
}

Use something like this for the clock:

NSTimer *timer = [NSTimer 
                  scheduledTimerWithTimeInterval: 1 
                  target: self 
                  selector: @selector(updateTimeLabel:) 
                  userInfo: nil 
                  repeats: YES
                  ];

[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];

Which triggers this function every second:

-(void)updateTimeLabel:(NSTimer*)theTimer
{
    // Get current time and update the label.
}