Question

Given any NSDate, how would I get the dates for the last midnight and the next midnight?

Answer 1

This is surprisingly complex, but doable:

NSDate *date = ...;
NSUInteger componentFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents *parts = [[NSCalendar currentCalendar] components:componentFlags fromDate:date];
NSDateComponents *midnightComponents = [[NSDateComponents alloc] init];
[midnightComponents setDay:[parts day]];
[midnightComponents setMonth:[parts month]];
[midnightComponents setYear:[parts year]];
NSCalendar *cal = [[NSCalendar currentCalendar];
NSDate *midnight = [cal dateFromComponents:midnightComponents];

NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
[offsetComponents setDay:1];
NSDate *nextMidnight = [cal dateByAddingComponents:offsetComponents toDate: midnight options:0];

I think Apple’s design overcomplicated things a bit, compared to, say, .NET or even Java, but it is manageable.