objective-c - How execute function on fixed time on mac os x?

Question

I write a simple application for mac osx that works with system time to calculate some data, i want to run an specific routine every time clock come to 12:00
Is there any system api for this?
How i do this?

actually i have a status bar item in my app that show current day in month in any selected calendar like gregorian and islamic, and i want to this value will be sync with system time

Answer 1

如果您的例程是以下方法- routine:(NSTimer *)timer：object

NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate]; // Current time
NSTimeInterval then = ((int)now + 86400) % 86400; // Next 12am
NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:then];
NSTimer *timer = [[NSTimer alloc] initWithFireDate:date interval:86400 target:object @selector(routine:) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];