NSTimer run every minute but on first second - ios

Question

I have experience with NSTimer to run it once per minute, like
NSTimer.scheduledTimerWithTimeInterval(60.0, target: self, selector: Selector("everyMinute"), userInfo: nil, repeats: true)
Is it possible to use NSTimer, some other class, or some other control, to run some method every minute but on first second of minute ?
I do have some idea how to implement it on my own, but I am first checking is this already exist ?

Answer 1

One way would be to figure out the current next minute using an NSCalendar and schedule the timer to start from that, manually scheduling on the runLoop
let date = NSDate()
let calendar = NSCalendar.currentCalendar()
let components = calendar.components(NSCalendarUnit.CalendarUnitEra|NSCalendarUnit.CalendarUnitYear|NSCalendarUnit.CalendarUnitMonth|NSCalendarUnit.CalendarUnitDay|NSCalendarUnit.CalendarUnitHour|NSCalendarUnit.CalendarUnitMinute, fromDate: date)
components.minute += 1
components.second = 1
let nextMinuteDate = calendar.dateFromComponents(components)
let timer = NSTimer(fireDate: nextMinuteDate!, interval: 60, target: self, selector: Selector("everyMinute"), userInfo: nil, repeats: true)
NSRunLoop.mainRunLoop().addTimer(timer, forMode: NSDefaultRunLoopMode)

Answer 2

The accepted answer, updated for Swift 5:
let date = Date()
let calendar = Calendar.current
var components = calendar.dateComponents([.era, .year, .month, .day, .hour, .minute], from: date)
guard let minute = components.minute else { return }
components.second = 0
components.minute = minute + 1
guard let nextMinute = calendar.date(from: components) else { return }
let timer = Timer(fire: nextMinute, interval: 60, repeats: true) { [weak self] timer in
self?.everyMinute()
}
RunLoop.main.add(timer, forMode: .default)

Answer 3

The NSDate method timeIntervalSinceReferenceDate returns the number of seconds since January 1, 2001, at 12:00 a.m. GMT. It includes fractions of a second
If you call that, divide by 60, take the floor value, then multiply by 60, it should give you the time interval of the current "round minute". Add 60 to that, and you get the time interval for the next "round minute. Add 1 to THAT, and you get a time interval for one second after the next "round minute".
The code might look something like this:
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
NSTimeInterval nextMinute = floor(now/60)*60 + 61 //time interval for next minute, plus 1 second
NSTimeInterval delay = nextMinute - now;
//Delay now contains the number of seconds until the next "round minute", plus 1 second.
dispatch_after(
dispatch_time(DISPATCH_TIME_NOW,
(int64_t)(delay * NSEC_PER_SEC)),
dispatch_get_main_queue(), ^
{
//Replace the code below with whatever target/userInfo you need.
[NSTimer scheduledTimerWithTimeInterval: 60
target: self
userInfo: nil;
repeats: YES];
}
);
Edit: Actually, the "First second" of a minute is the zero'th second, so you should probably change the +61 in the code above that calculated nextMinute to "+60", not "+61"

Answer 4

A much simpler approach:
func everyMinute() {
// some code you want done every minute, in the first second, or VERY close to it
let delaySeconds = 60 - NSDate.timeIntervalSinceReferenceDate.truncatingRemainder(dividingBy: 60)
Timer.scheduledTimer(withTimeInterval: delaySeconds, repeats: false) { timer in
self.everyMinute()
}
}