How do I get the current date in Cocoa

Question

I m getting started developing for the iPhone and as such I am looking at different tutorials online as well as trying some different things out myself  Currently  I m trying to create a countdown until midnight  To get the number of hour  minutes  and seconds  I do the following  which I found somewhere    NSDate  now    NSDate date    int hour   23 -   now dateWithCalendarFormat nil timeZone nil  hourOfDay   int min   59 -   now dateWithCalendarFormat nil timeZone nil  minuteOfHour   int sec   59 -   now dateWithCalendarFormat nil timeZone nil  secondOfMinute   countdownLabel text    NSString stringWithFormat    02d  02d  02d   hour  min sec     However  each place I use -dateWithCalendarFormat timeZone  I get the following error   warning   NSDate  may not respond to  -dateWithCalendarFormat timeZone    Messages without a matching method signature will be assumed to return  id  and accept       as arguments   warning  no  -hourOfDay  method found error  invalid operands to binary -  have  int  and  id     This seems like something very simple  What am I missing   Also  I ve noticed at different places and at different times the asterisk     is located either right after the time NSDate  now or right before the variable NSDate  now  What is the difference in the two and why would you use one versus the other

User · Answer

It took me a while to locate why the sample application works but mine don't.

The library (Foundation.Framework) that the author refer to is the system library (from OS) where the iphone sdk (I am using 3.0) is not support any more.

Therefore the sample application (from about.com, http://www.appsamuck.com/day1.html) works but ours don't.

User · Answer

CFGregorianDate currentDate   CFAbsoluteTimeGetGregorianDate CFAbsoluteTimeGetCurrent    CFTimeZoneCopySystem     countdownLabel text    NSString stringWithFormat    02d  02d  2 0f   currentDate hour  currentDate minute  currentDate second     Mark was right this code is MUCH more efficient to manage dates hours min and secs  But he forgot the   at the beginning of format string declaration

User · Answer

NSDate  now and NSDate  now are the same thing  a pointer to an NSDate object   You probably want to use descriptionWithCalendarFormat timeZone locale  rather than dateWithCalendarFormat      the latter returns an NSCalendarDate  which the docs say is scheduled to be deprecated at some point

User · Answer

Original poster - the way you re determining seconds until midnight won t work on a day when daylight savings starts or ends  Here s a chunk of code which shows how to do it    It ll be in number of seconds  an NSTimeInterval   you can do the division modulus etc to get down to whatever you need    NSDateComponents  dc     NSCalendar currentCalendar  components NSDayCalendarUnit NSMonthCalendarUnit NSYearCalendarUnit fromDate  NSDate date     dc setDay dc day   1   NSDate  midnightDate     NSCalendar currentCalendar  dateFromComponents dc   NSLog   Now      Tonight Midnight      Hours until midnight    1f    NSDate date   midnightDate   midnightDate timeIntervalSinceDate  NSDate date     60 0   60 0

User · Answer

You can also use    CFGregorianDate currentDate   CFAbsoluteTimeGetGregorianDate CFAbsoluteTimeGetCurrent    CFTimeZoneCopySystem     countdownLabel text    NSString stringWithFormat    02d  02d  02 0f   currentDate hour  currentDate minute  currentDate second   CFRelease currentDate      Don t forget this  VERY important   I think this has the following advantages    No direct memory allocation  Seconds is a double instead of an integer  No message calls  Faster

User · Answer

Here s another way   NSDate  now    NSDate date      maybe not 100  approved  but it works in English   You could localize if necessary NSDate  midnight    NSDate dateWithNaturalLanguageString   midnight tomorrow        num of seconds between mid and now NSTimeInterval timeInt    midnight timeIntervalSinceDate now   int hours    int  timeInt 3600  int minutes     int  timeInt   3600    60  int seconds    int  timeInt   60    You lose subsecond precision with the cast of the NSTimeInterval to an int  but that shouldn t matter

User · Answer

You must use the following   NSCalendar  gregorian     NSCalendar alloc  initWithCalendarIdentifier NSGregorianCalendar   NSDateComponents  dateComponents    gregorian components  NSHourCalendarUnit    NSMinuteCalendarUnit   NSSecondCalendarUnit  fromDate yourDateHere   NSInteger hour    dateComponents hour   NSInteger minute    dateComponents minute   NSInteger second    dateComponents second    gregorian release     There is no difference between NSDate  now and NSDate  now  it s just a matter of preference  From the compiler perspective  nothing changes

User · Answer

Replace this   NSDate  now    NSDate date   int hour   23 -   now dateWithCalendarFormat nil timeZone nil  hourOfDay   int min   59 -   now dateWithCalendarFormat nil timeZone nil  minuteOfHour   int sec   59 -   now dateWithCalendarFormat nil timeZone nil  secondOfMinute   countdownLabel text    NSString stringWithFormat    02d  02d  02d   hour  min sec     With this   NSDate  now    NSDate date   NSCalendar  gregorian     NSCalendar alloc  initWithCalendarIdentifier NSGregorianCalendar   NSDateComponents  dateComponents    gregorian components  NSHourCalendarUnit    NSMinuteCalendarUnit   NSSecondCalendarUnit  fromDate now   NSInteger hour    dateComponents hour   NSInteger minute    dateComponents minute   NSInteger second    dateComponents second    gregorian release   countdownLabel text    NSString stringWithFormat    02d  02d  02d   hour  minute  second

User · Answer

You need to do something along the lines of the following   NSDate  now    NSDate date   NSCalendar  calendar    NSCalendar currentCalendar   NSDateComponents  components    calendar components NSHourCalendarUnit fromDate now   NSLog    d    components hour      And so on

User · Answer

you can get current date time with the following code       NSDate  date    NSDate date       NSDateFormatter  formatter     NSDateFormatter alloc  init       NSTimeZone  destinationTimeZone    NSTimeZone systemTimeZone       formatter timeZone   destinationTimeZone       formatter setDateStyle NSDateFormatterLongStyle        formatter setDateFormat   MM dd yyyy hh mma        NSString  dateString    formatter stringFromDate date

User · Answer

Also  I ve noticed at different places and at different times the asterisk     is located either right after the time NSDate  now or right before the variable NSDate  now  What is the difference in the two and why would you use one versus the other    The compiler doesn t care  but putting the asterisk before the space can be misleading  Here s my example   int  a  b    What is the type of b   If you guessed int    you re wrong  It s just int   The other way makes this slightly clearer by keeping the   next to the variable it belongs to   int  a  b    Of course  there are two ways that are even clearer than that   int b   a   int  a  int b

User · Answer

You have problems with iOS 4 2  Use this Code   NSDate  currDate    NSDate date   NSDateFormatter  dateFormatter     NSDateFormatter alloc init    dateFormatter setDateFormat   dd MM YY HH mm ss    NSString  dateString    dateFormatter stringFromDate currDate   NSLog       dateString     -- 20 01 2011 10 36 02

User · Answer

There is no difference in the location of the asterisk  at in C  which Obj-C is based on  it doesn t matter    It is purely preference  style

User · Answer

NSString   displayCurrentTimeWithAMPM        NSDateFormatter  outputFormatter     NSDateFormatter alloc  init        outputFormatter setDateFormat   h mm aa         NSString  dateTime    NSString stringWithFormat        outputFormatter stringFromDate  NSDate date          return dateTime      return 3 33 AM

[objective-c] How do I get the current date in Cocoa

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