Week based calendar and iOS

This talk covers some aspects of working with dates, calendars in iOS and SQLite

Transcript

1. Dodatko Alexander November 2012
3. How many months does the year consist of?
4. What is the first day of the year?
5. What day does a new week start on?
6. Right, but did you know that ...
7. Jewish calendar consists of 13 months. And month #6 is a leaping one.
8. In Japan the calendar may return to year #1 at the day of the emperor's death
9. In Russia week starts on Monday. In the USA the first day is Sunday
11. Dates must look in the way the user expects
14. -(NSDate*)parseDate:( NSString* )date_ { NSDateFormatter* df_ = [ NSDateFormatter new ]; df_.dateFormat = @"yyyy-MM-dd"; return [ df_ dateFromString: date_ ]; } The Typical Solution
15. -(NSDate*)parseDate:( NSString* )date_ { NSDateFormatter* df_ = [ NSDateFormatter new ]; df_.dateFormat = @"yyyy-MM-dd"; return [ df_ dateFromString: date_ ]; } WRONG !
17. Use en_US_POSIX locale for dates from the network Use Gregorian calendar too
19. Do not forget to set the same Locale for both NSCalendar and NSDateFormatter
20. Or let my library do it for you dodikk / ESLocale
21. Ok. How about SQLite?
23. SELECT SUM( Visits) FROM VisitsLog WHERE Date BETWEEN x AND y GROUP BY week
24. What should I take as week ?
25. SELECT SUM( Visits) FROM VisitsLog WHERE Date BETWEEN x AND y GROUP BY Strftime('%Y-%W', Date )
26. SELECT SUM( Visits) FROM VisitsLog WHERE Date BETWEEN x AND y GROUP BY Strftime('%Y-%W', Date )
28. SELECT SUM( Visits) FROM VisitsLog WHERE Date BETWEEN x AND y GROUP BY ObjcFormatDate('YYYY-ww', Date, 'en_US_POSIX' )
30. int sqlite3_create_function( dbHandle, "ObjcFormatDate", 3, //int nArg, SQLITE_UTF8, NULL, // sqlite user data functionPointer, NULL, NULL // for aggregates );
31. Plan of attack Convert C strings to NSString Convert date string to NSDate Format NSDate using locale
32. SQLite uses ANSI format yyyy-MM-dd
33. Demo
34. One More Thing
36. 1000 times slower than strftime 10K records Creating NSDateFormatter on-the-fly
38. Same speed as strftime Same 10K records Singletone NSDateFormatter
39. Thread Safety
40. dodikk / ESLocale
41. Contacts Oleksandr Dodatko mail/jabber : dodikk88.tutor@gmail.com Skype : alexander.dodatko.work Twitter : @dodikk88 Github : https://github.com/dodikk https://github.com/EmbeddedSources