does anyone know why i'm getting a null date value after putting this thru my date formatter?
//Sets expire date for listing to String
NSString *expireDate = [[_itemDetailArray valueForKey:#"expireDate"]description]; //returns my date correctly
NSString *formattedStringDate = [NSString stringWithFormat:#"%#",[formatter dateFromString:expireDate]]; //comes out null
Any ideas why?
Your formatter's format is wrong. Try with this
[formatter setDateFormat:#"yyyy-MM-dd hh:mm:ss zzz"];
Related
i have a problem to convert string date (maybe ISO 8601) to NSDate..
NSString *testDate = #"2016-01-27T18:28:53.344+01:00";
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
[formatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.sssZZZZZ"];
NSLog(#"_date_: %#",[formatter dateFromString:testDate]);
NSLog(#"_now_date: %#",[formatter stringFromDate:[NSDate date]]);
NSLog return:
_date_:(null)
_now_date: 2016-02-03T22:36:46.046+01:00
What is the right time format ? if log current date the format maybe appear correct but i can't get NSDate from string
You have fractional second in your date string. Fractional seconds are designated capital S. Try this:
[formatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ"]
Note that the NSDate you get back is 2016-01-27 17:28:53.344 +0000. This is due to NSDate always represent time in UTC. 17:38 UTC is the same moment in time as 18:38 +01:00.
I want to do is produce a simple NSDate date in addition to would like
to add methods to add and subtract.
Date * myDate = [NSDate date]; // today
NSLog ("10 days after:%#", [myDate addToDays: 10]);
================= category ==================
#implementation NSDate (AddDate)
- (NSDate *)addToDays:addToDays{
NSDate *returnDate = [***HowGetmyDate*** dateByAddingTimeInterval:60*60*24*addToDays];
return returnDate;
}
how get (myDate)?
The base date need not necessarily today.
Just use self to get your date object.
Category is the extension of the original class, you can operate/implement it as the original one.
#implementation NSDate (AddDate)
- (NSDate *)addToDays:addToDays{
NSDate *returnDate = [self dateByAddingTimeInterval:60*60*24*addToDays];
return returnDate;
}
I have a coreData model already setup and data added to it. I want to search for all items from the last 30 days, and then add together a total number of units.
Here's what I got :-
- (void) calculateThirtyDayValues {
NSDate *endDate = [NSDate date];
NSTimeInterval timeSinceRefDate = [NSDate timeIntervalSinceReferenceDate];
NSTimeInterval lastThirtyDays = timeSinceRefDate- 2592000;
NSDate *startDate = [NSDate dateWithTimeIntervalSinceReferenceDate:lastThirtyDays];
NSPredicate *predicate = [NSPredicate predicateWithFormat: #"(date >= %#) AND (date <= %#)", startDate, endDate];
}
Basically I have create an NSDate object set todays date, and then created another NSDate object set to 30 days before today. Then trying to predicate all objects from the start date until the present date.
I am getting results returned, but they don't seem to be really matching up with what the totals should be for the past 30 days. It appears to just be returning everything!
Any ideas?
Your predicate seems to be OK, but your date code is incorrect, for a couple of reasons.
[NSDate date] returns the current date, with sub-millisecond precision. So if you create the predicate at 4:15:37 PM local time, this predicate would not find any objects with a date of 5:37:42 PM local time. If you want down-to-the-second precision like that, then you're probably OK. But if you want granularity to a different calendar unit (such as by day), then you need to do more work.
Not every day has 86,400 seconds in it. Thus your attempt to subtract (30*86400) is subtly wrong. You should be letting the calendar object do the math for you:
NSDate *endDate = ...;
NSDateComponents *diff = [[NSDateComponents alloc] init];
[diff setDay:-30];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *startDate = [calendar dateByAddingComponents:diff toDate:endDate options:0];
Am sorry to ask such a trivial question. Am a newbie to Objective-C, & simply cannot see how to get this working, after having tried several possible ways & google'd around for it. Please help!
My question is simple. I have a class-level NSDate object, which is declared outside any method in the class as:
NSDate *fromDate;
Now, within a method, am setting this value to the date from a DatePicker as:
fromDate = [datePicker date];
Soon after the above assignment, I print its value into the log & it works fine.
NSLog(#"From Date: %#", fromDate);
Now, when I use NSDate's value in another/different method, the value's gone! Why is it not persisted across methods in the same class itself? What can I do for the value to be accessible across methods?
Thanks for your reply.
Hi Remy,
I didn't know Objective-C didn't have class-level variables! Thanks for pointing it out!
Yes, I've set the project (in Xcode) to do ARC (so, I believe that should take care).
Here is the code:
In ViewController.h
....
....
#property (nonatomic, retain) NSDate *historyFromDate;
#property (nonatomic, retain) NSDate *historyToDate;
....
....
-(IBAction) fromDateChosen: (id)sender;
-(void) fetchTheHistory;
In ViewController.m
...
...
#synthesize historyFromDate;
#synthesize historyToDate;
....
....
-(IBAction) fromDateChosen: (id)sender {
NSString *buttonTitle = #"I've chosen the 'FROM' date";
if ([[buttonDateChosen currentTitle] isEqualToString:buttonTitle]) {
NSLog(#"User has chosen the 'From' date");
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
[dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
// Get the chosen date value
NSDate *fromDate = [datePicker date];
historyFromDate = fromDate;
// Set the 'to' date label to reflect the user's choice
labelFromDate.text = [dateFormatter stringFromDate:historyFromDate];
NSLog(#"'From' Date Chosen:%#", historyFromDate);
//[dateFormatter stringFromDate:[datePicker date]]);
[self fetchTheMoodHistory];
}
}
...
...
...
-(void) fetchTheHistory {
NSLog(#"Calling fetchTheHistory for the period from %#", historyFromDate);
...
...
}
...
...
fromDateChosen gets called after the user chooses a date form a Date Picker object in the UI.
Within the method 'fromDateChosen', when I print the historyFromDate, the value is correct.
But, when I print it in fetchTheHistory method, the value shows the current date/time (not the one the user chose).
The date property of UIDatePicker is retained by that class, and will be accessible as long as the date picker itself is in scope and valid (not been released). You are storing this date value in a variable, but not retaining it yourself, so when the date picker goes out of scope you lose the value. As a quick fix, do this instead;
fromDate = [[datePicker date] retain];
Now, this is not the best approach, you really should be making the date a property of whatever class is using this information.
Try put the fromDate variable under class scope, e.g:
#implementation ViewController
{
NSDate *fromDate;
}
I'm using a UIDatePicker and I'm having problems with converting this data to a System.DateTime value in MonoTouch. There are problems with conversions from NSDate to DateTime, which I've mostly solved, but now I see that if you choose a date that is NOT in the same Daylight Savings Time period then you are an hour off. For example, if I pick a date in January 2010 I'll have an offset issue.
What I'd like to do is when a user selects a date/time from the UIDatePicker is to get the Year, Month, Day, Hour, and Minute values of the NSDate and just create a New System.DateTime with those values and I'll always be assured to get a date value exactly as the user see's it in the UIDatePicker.
How can I break down a NSDate value into the various date parts?
Thank you.
An easy way to get rid of the daylight saving time problems is to set the time zone to GMT. Then the UIDatePicker will ignore daylight saving time:
_datePicker.TimeZone = NSTimeZone.FromAbbreviation("GMT");
Implicit conversion of NSDate to and from DateTime is quite good in Monotouch, but you must be aware that NSDate is always an UTC time and DateTime is default set to DateTimeKind.Unspecified (when read from database) or DateTimeKind.Locale (when set with DateTime.Today).
The best way to convert without complicated time-zone computations is to force the right DateTimeKind:
// Set date to the date picker (_date is a DateTime with time part 0:00:00):
_datePicker.Date = DateTime.SpecifyKind(_date, DateTimeKind.Utc);
// Get the date from the date picker:
_date = DateTime.SpecifyKind(_datePicker.Date, DateTimeKind.Unspecified);
This is easier and more reliable than getting the individual Day, Month and Year values.
It appears this can be done using an instance of NSDateComponents. The following has been copied from Date Components and Calendar Units:
To decompose a date into constituent
components, you use the NSCalendar
method components:fromDate:. In
addition to the date itself, you need
to specify the components to be
returned in the NSDateComponents
object. For this, the method takes a
bit mask composed of Calendar Units
constants. There is no need to specify
any more components than those in
which you are interested. Listing 3
shows how to calculate today’s day and
weekday.
Listing 3 Getting a date’s components
NSDate *today = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *weekdayComponents = [gregorian components:(NSDayCalendarUnit | NSWeekdayCalendarUnit) fromDate:today];
NSInteger day = [weekdayComponents day];
NSInteger weekday = [weekdayComponents weekday];
public static DateTime NSDateToDateTime(MonoTouch.Foundation.NSDate date)
{
return (new DateTime(2001,1,1,0,0,0)).AddSeconds(date.SecondsSinceReferenceDate);
}
public static MonoTouch.Foundation.NSDate DateTimeToNSDate(DateTime date)
{
return MonoTouch.Foundation.NSDate.FromTimeIntervalSinceReferenceDate((date-(new DateTime(2001,1,1,0,0,0))).TotalSeconds);
}
Ok by using the above code you can turn the NSDate into a DateTime an do as you normally do on .Net World :) then with > DateTimeToNSDate you can revert it to a NSDate
hope this helps
Alex