问题
I want to make a UILocalNotification repeat every week, before iOS7 I would use localNotification.repeatInterval = NSWeekCalendarUnit - except NSWeekCalendarUnit has been deprecated.
The docs say:
"Use NSCalendarUnitWeekOfMonth or NSCalendarUnitWeekOfYear, depending on which you mean"
But I don't know what the difference is, so I don't know which one I mean.
回答1:
These don't appear to be documented but most likely NSCalendarUnitWeekOfYear will be a value from 1-53 (or maybe 0-52) representing the week number within the calendar year while NSCalendarUnitWeekOfMonth will be 1-5 (or maybe 0-4) representing the week within the month.
This all assumes Gregorian calendar. I can't speak to other calendar types.
It seems that NSCalendarUnitWeekOfMonth is equal to kCFCalendarUnitWeekOfMonth which is defined as "Specifies the original week of a month calendar unit." and NSCalendarUnitWeekOfYear is equal to kCFCalendarUnitWeekOfYear which is defined as "Specifies the original week of the year calendar unit.".
回答2:
As for the UILocalNotification
NSCalendarUnitWeekOfYear should be used as a unit for repeatInterval.
When I set repeatInterval = NSCalendarUnitWeekOfMonth for the notification scheduled 10 seconds from now, the notification doesn't fire, and the description of the instance of UILocalNotification prints .. next fire date = (null) ...
If I use NSCalendarUnitWeekOfYear then notification appears and I see correct next fire date from code in the notification's description.
来源：https://stackoverflow.com/questions/22341048/difference-between-nscalendarunitweekofyear-nscalendarunitweekofmonth