basically I am trying to store todays date but every time I try to do that NSDate returns nil to me
self.calendarView.selectedDate = [NSDate date];
I am new to objective-c so maybe I am doing something wrong here but it seems fairly straight forward.
[NSDate date] will return a correct date. Check if your self.calendarView is not nil at this point by doing:
NSLog(#"calendar: %#", self.calendarView);
NSDate *now = [NSDate date];
NSLog(#"now: %#", now);
self.calendarView.selectedDate = now;
Related
In Objective-C, how to test if today is not after a specific date?
I am using the following way but am curious if there is a better way or other alternatives to go about this.
NSString *dateString = #"20140928";
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"yyyyMMdd"];
NSDate *expirationDate = [dateFormat dateFromString:dateString];
NSDate *today = [NSDate date];
if ([today laterDate:expirationDate] != today) {
NSLog(#"Today is not after expirationDate");
}
Most of your code is getting the expiration date so that doesn't really count.
Once you have the date then using laterDate: or compare: with [NSDate date] are two simple ways.
You could also do:
if ([expirationDate timeIntervalSinceNow] > 0) {
// expiration date is after "now"
}
This avoids the need to use [NSDate date].
As an alternative there is:
if ([today compare:expirationDate] == NSOrderedAscending)
// expirationDate comes "after" today
if ([today compare:expirationDate] == NSOrderedDescending)
// expirationDate comes "before" today
if ([today compare:expirationDate] == NSOrderedSame)
// expirationDate equals today
Here is the set up, I have a JSON feed I am using and I want to find the difference between two specific dates called posted_date and planned_expiration_date. They are in an odd format I so I thought I could truncate them down to just the date.I could then use NSTimeInterval to find the difference in seconds.
// Time Interval Left
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
NSString *startDate = [firstPerson objectForKey:#"posted_date"];
NSString *endDate = [firstPerson objectForKey:#"planned_expiration_date"];
//Ammend the strings to YYYY-MM-DD
[formatter setDateFormat:#"yyyy-mm-dd"];
int newlength = 9;
NSDate *startDateAmmended =[formatter dateFromString:[startDate substringFromIndex:newlength]];
NSDate *endDateAmmended = [formatter dateFromString:[endDate substringFromIndex:newlength]];
Here is the bit I'm not too sure about. The date appears something like this "2013-06-07T13:40:01Z" straight from the feed. I don't know how to deal with the T and Z chars in the date formatter method so I truncate the string with substringFromIndex to make it 10 chars and then attempted the following code.
//Difference in Date
NSTimeInterval *startDifference = [startDateAmmended timeIntervalSinceNow];
NSTimeInterval *endDifference = [endDateAmmended timeIntervalSinceNow];
NSTimeInterval timeDifferenceInSeconds = startDifference - endDifference;
I get the following error, .../JSONParser/ViewController.m:52:21: Initializing 'NSTimeInterval *' (aka 'double *') with an expression of incompatible type 'NSTimeInterval' (aka 'double') at the first two calls to NSTimeInterval.
I am sure I'm going wrong in a few places and I'm sure this isn't the easiest method of doing it. Could anyone recommend how I would fix this issue or an easier way to go about getting the differences between dates?
Your error comes from your lines that say:
NSTimeInterval *startDifference = [startDateAmmended timeIntervalSinceNow];
NSTimeInterval *endDifference = [endDateAmmended timeIntervalSinceNow];
They should be:
NSTimeInterval startDifference = [startDateAmmended timeIntervalSinceNow];
NSTimeInterval endDifference = [endDateAmmended timeIntervalSinceNow];
Or, more simply, don't define those two difference variables at all, and just use:
NSTimeInterval timeDifferenceInSeconds = [endDateAmmended timeIntervalSinceDate:startDateAmmended];
To calculate the difference between two ISO 8601 / RFC 3339 date strings, you can do:
NSDate *startDate = [self dateFromISO8601String:#"2013-06-01T16:27:35Z"];
NSDate *endDate = [self dateFromISO8601String:#"2013-06-07T13:40:01Z"];
NSTimeInterval elapsed = [endDate timeIntervalSinceDate:startDate];
NSLog(#"Time elapsed (in seconds) is %.0f", elapsed);
where dateFromISO8601String is defined as:
- (NSDate *)dateFromISO8601String:(NSString *)string
{
static NSDateFormatter *formatter = nil;
if (formatter == nil)
{
formatter = [[NSDateFormatter alloc] init];
NSLocale *enUSPOSIXLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
formatter.locale = enUSPOSIXLocale;
formatter.dateFormat = #"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'";
formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
}
return [formatter dateFromString:string];
}
You can get the difference in seconds between two NSDate objects like this:
double difference = [startDateAmmended timeIntervalSinceDate:endDateAmmended];
Note that with the substring operation you don't have the time, only the date, so the difference will be in seconds but with steps of whole days.
I need to display the current Date and Time.
I have used ;
NSDate *currentDateNTime = [NSDate date];
I want to have the current date and time (Should display the system time and not GMT time).
The output should be in a NSDate format and not NSString.
for example;
NSDate *currentDateNTime = [NSDate date];
// Do the processing....
NSDate *nowDateAndTime = .....; // Output should be a NSDate and not a NSString
Since all NSDate is GMT referred, you probably want this:
(don'f forget that the nowDate won't be the actual current system date-time, but it's "shifted", so if you will generate NSString using NSDateFormatter, you will see a wrong date)
NSDate* currentDate = [NSDate date];
NSTimeZone* currentTimeZone = [NSTimeZone timeZoneWithAbbreviation:#"GMT"];
NSTimeZone* nowTimeZone = [NSTimeZone systemTimeZone];
NSInteger currentGMTOffset = [currentTimeZone secondsFromGMTForDate:currentDate];
NSInteger nowGMTOffset = [nowTimeZone secondsFromGMTForDate:currentDate];
NSTimeInterval interval = nowGMTOffset - currentGMTOffset;
NSDate* nowDate = [[NSDate alloc] initWithTimeInterval:interval sinceDate:currentDate];
Every moment in time is the same moment in time everywhere around the world —- it is just expressed as different clock times in different timezones. Therefore, you can't change the date to some other date that represents the time in your timezone; you must use an NSDateFormatter that you feed with the timezone you are in. The resulting string is the moment in time expressed in the clock time of your position.
Do all needed calculations in GMT, and just use a formatter for displaying.
Worth reading
Does [NSDate date] return the local date and time?
Some useful resources for anyone coming to this more recently:
Apple date and time programming guide do read it if you're doing anything serious with dates and times.
https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/DatesAndTimes/DatesAndTimes.html#//apple_ref/doc/uid/10000039i?language=objc
Useful category on NSDate with lots of utilities does allow a ~new~ date to be generated based on an existing date.
https://github.com/erica/NSDate-Extensions
There's also a swift version of the category
https://github.com/erica/SwiftDates
You need an NSDateFormatter and call stringFromDate this method to get a string of your date.
NSDateFormatter *dateformater = [[NSDateFormatter alloc] init];
[dateformater setDateFormat:#"yyyyMMdd,HH:mm"];
NSString *str = [dateformater stringFromDate: currentDateNTime];
use this method
-(NSDate *)convertDateToDate:(NSDate *) date
{
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
NSDate *nowDate = [[[NSDate alloc] init] autorelease];
[formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
[formatter setDateFormat:#"yyyy-MM-d H:m:s"];
NSString * strdate = [formatter stringFromDate:date];
nowDate = [formatter dateFromString:strdate];
return nowDate;
}
this may return you what you want.
i hope you this may help you.
I want to get the current date using [NSDate date] in a While Loop. I accomplish this by doing like this:
while (interval > 0.0) {
NSDate *currentDate = [[NSDate alloc] init];
currentDate = [NSDate date];
interval = (float) [newDate timeIntervalSinceDate: currentDate] / 60;
[currentDate release];
}
I dont know why is the Memory leaks shows that there is a great amount of memory is leaked. Kindly guide me that what is the right way to accomplish my task.
In line NSDate *currentDate = [[NSDate alloc] init]; you create a new object, which you should release. In line currentDate = [NSDate date]; you do not release an old object, you only make a pointer to point to another object. In line [currentDate release]; you release an object created on the second line of a loop, which may cause an error (that object is marked as autorelease one and iOS will clean it for you). You should rewrite your code like:
while (interval > 0.0) {
NSDate *currentDate = [NSDate date];
interval = (float) [newDate timeIntervalSinceDate: currentDate] / 60;
}
You don't need the first line NSDate *currentDate = [[NSDate alloc] init];. You can directly assign the [NSDate date] to currentDate.
NSDate *currentDate = nil;
while (interval > 0.0) {
currentDate = [NSDate date];
interval = (float) [newDate timeIntervalSinceDate: currentDate] / 60;
}
The problem is not that you are leaking per se but that you are running in a while loop.
The auto released dates are growing in the autorelease pool because the pool only empties in the idle time on the run loop.
One solution is to create a local autorelease pool within the scope of the while
while (foo) {
NSAutoreleasePool *aPool = [[NSAutoreleasePool alloc ] init];
NSDate *currentDate = [NSDate date];
// other computational foo
[aPool release]
}
When you release the pool in the local scope it will immediately drop the autoreleased date you requested.
I have a NSDate that I must compare with other two NSDate and I try with NSOrderAscending and NSOrderDescending but if my date is equal at other two dates?
Example: if I have a myDate = 24/05/2011 and other two that are one = 24/05/2011 and two 24/05/2011 what can I use?
According to Apple documentation of NSDate compare:
Returns an NSComparisonResult value that indicates the temporal ordering of the receiver and another given date.
- (NSComparisonResult)compare:(NSDate *)anotherDate
Parameters anotherDate
The date with which to compare the
receiver. This value must not be nil.
If the value is nil, the behavior is
undefined and may change in future
versions of Mac OS X.
Return Value
If:
The receiver and anotherDate are
exactly equal to each other,
NSOrderedSame
The receiver is later in
time than anotherDate,
NSOrderedDescending
The receiver is
earlier in time than anotherDate,
NSOrderedAscending
In other words:
if ([date1 compare:date2] == NSOrderedSame) ...
Note that it might be easier in your particular case to read and write this :
if ([date2 isEqualToDate:date2]) ...
See Apple Documentation about this one.
After searching, I've got to conclusion that the best way of doing it is like this:
- (BOOL)isEndDateIsSmallerThanCurrent:(NSDate *)checkEndDate
{
NSDate* enddate = checkEndDate;
NSDate* currentdate = [NSDate date];
NSTimeInterval distanceBetweenDates = [enddate timeIntervalSinceDate:currentdate];
double secondsInMinute = 60;
NSInteger secondsBetweenDates = distanceBetweenDates / secondsInMinute;
if (secondsBetweenDates == 0)
return YES;
else if (secondsBetweenDates < 0)
return YES;
else
return NO;
}
You can change it to difference between hours also.
If you want to compare date with format of dd/MM/yyyy only, you need to add below lines between NSDate* currentdate = [NSDate date]; && NSTimeInterval distance
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"dd/MM/yyyy"];
[dateFormatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]
autorelease]];
NSString *stringDate = [dateFormatter stringFromDate:[NSDate date]];
currentdate = [dateFormatter dateFromString:stringDate];
I take it you are asking what the return value is in the comparison function.
If the dates are equal then returning NSOrderedSame
If ascending ( 2nd arg > 1st arg ) return NSOrderedAscending
If descending ( 2nd arg < 1st arg ) return NSOrderedDescending
I don't know exactly if you have asked this but if you only want to compare the date component of a NSDate you have to use NSCalendar and NSDateComponents to remove the time component.
Something like this should work as a category for NSDate:
- (NSComparisonResult)compareDateOnly:(NSDate *)otherDate {
NSUInteger dateFlags = NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit;
NSCalendar *gregorianCalendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDateComponents *selfComponents = [gregorianCalendar components:dateFlags fromDate:self];
NSDate *selfDateOnly = [gregorianCalendar dateFromComponents:selfComponents];
NSDateComponents *otherCompents = [gregorianCalendar components:dateFlags fromDate:otherDate];
NSDate *otherDateOnly = [gregorianCalendar dateFromComponents:otherCompents];
return [selfDateOnly compare:otherDateOnly];
}
NSDate actually represents a time interval in seconds since a reference date (1st Jan 2000 UTC I think). Internally, a double precision floating point number is used so two arbitrary dates are highly unlikely to compare equal even if they are on the same day. If you want to see if a particular date falls on a particular day, you probably need to use NSDateComponents. e.g.
NSDateComponents* dateComponents = [[NSDateComponents alloc] init];
[dateComponents setYear: 2011];
[dateComponents setMonth: 5];
[dateComponents setDay: 24];
/*
* Construct two dates that bracket the day you are checking.
* Use the user's current calendar. I think this takes care of things like daylight saving time.
*/
NSCalendar* calendar = [NSCalendar currentCalendar];
NSDate* startOfDate = [calendar dateFromComponents: dateComponents];
NSDateComponents* oneDay = [[NSDateComponents alloc] init];
[oneDay setDay: 1];
NSDate* endOfDate = [calendar dateByAddingComponents: oneDay toDate: startOfDate options: 0];
/*
* Compare the date with the start of the day and the end of the day.
*/
NSComparisonResult startCompare = [startOfDate compare: myDate];
NSComparisonResult endCompare = [endOfDate compare: myDate];
if (startCompare != NSOrderedDescending && endCompare == NSOrderedDescending)
{
// we are on the right date
}
Check the following Function for date comparison first of all create two NSDate objects and pass to the function:
Add the bellow lines of code in viewDidload or according to your scenario.
-(void)testDateComaparFunc{
NSString *getTokon_Time1 = #"2016-05-31 03:19:05 +0000";
NSString *getTokon_Time2 = #"2016-05-31 03:18:05 +0000";
NSDateFormatter *dateFormatter=[NSDateFormatter new];
[dateFormatter setDateFormat:#"yyyy-MM-dd hh:mm:ss Z"];
NSDate *tokonExpireDate1=[dateFormatter dateFromString:getTokon_Time1];
NSDate *tokonExpireDate2=[dateFormatter dateFromString:getTokon_Time2];
BOOL isTokonValid = [self dateComparision:tokonExpireDate1 andDate2:tokonExpireDate2];}
here is the function
-(BOOL)dateComparision:(NSDate*)date1 andDate2:(NSDate*)date2{
BOOL isTokonValid;
if ([date1 compare:date2] == NSOrderedDescending) {
//"date1 is later than date2
isTokonValid = YES;
} else if ([date1 compare:date2] == NSOrderedAscending) {
//date1 is earlier than date2
isTokonValid = NO;
} else {
//dates are the same
isTokonValid = NO;
}
return isTokonValid;}
Simply change the date and test above function :)