I use some code to translate a list of dates into different sections by month:
- (NSString *) calculateSectionPeriod{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSCalendarUnitYear | NSCalendarUnitMonth) fromDate: [self userDate]];
NSString *tmp = [NSString stringWithFormat:#"%ld", ([components year] * 1000) + [components month]];
NSLog(#"Section period = %#", tmp);
return tmp;
}
The userDate is set from a NSDatePicker.
In most cases, this prints strings like "2015006" (June 2015) or "2017011" (November 2017). However, in some cases, for some users of my app, it ends up printing "15003" (and ends up causing some problems in Core Data). This is coming from their own reports, and I haven't been able to reproduce the issue on my own device, but it's clear to me that the problem is with this code.
Any reason where the 'year' component would print '15' instead of of '2015'? Is it by region or some language settings? I've tried setting different regions and languages, but haven't been able to reproduce the problem myself.
Related
I want to "hardcode" an expiration date into my beta code. Right now I manually calculate a unix date and compare that to the current date time:
if([[NSDate date] timeIntervalSince1970]>1422748800) mustHalt = TRUE;
I'd like a way of replacing the 1422748800 with a macro that generates the equivalent number for a date 90 days in the future at compile time.
Any suggestions?
The predefined macro __DATE__ is what you need. Here is a SO question related to this. But maybe you want to use a code like this:
const int daysToExpire = 14;
NSString *compileDate = [NSString stringWithUTF8String:__DATE__];
NSDateFormatter *df = [[NSDateFormatter alloc] init];
[df setDateFormat:#"MMM d yyyy"];
NSLocale *usLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US"];
[df setLocale:usLocale];
NSDate *expireDate = [df dateFromString:compileDate];
bool isExpired = ([[NSDate date] compare:expireDate] == NSOrderedDescending); // decide for it
In my App, When i select a day in the datepicker it should automatically calculate and display 4 other days and also it should notify on the corresponding days. For Eg. if i enter 19-08-2014, it should calculate and display the 3rd day, the 7th day, the 14th day and the 21st day from 19-08-2014(the day i entered in datepicker).
How would i achieve this. Any help would be greatly appreciated.
I have added my current code for your reference. This doesnt serve my purpose.
Kindly Help.
(IBAction)save:(UIButton *)sender {
NSDate *pickerDate = [self.picker date];
UILocalNotification *localNotif = [[UILocalNotification alloc]init];
//localNotif.alertBody = _enterText.text;
localNotif.alertBody = #"Please Take Your Rabipur Dosage";
localNotif.fireDate = pickerDate;
localNotif.timeZone = [NSTimeZone defaultTimeZone];
localNotif.soundName = (UILocalNotificationDefaultSoundName);
localNotif.applicationIconBadgeNumber = 1;
//localNotif.repeatInterval = NSDayCalendarUnit;
[[UIApplication sharedApplication]scheduleLocalNotification:localNotif];
[self dismissViewControllerAnimated:YES completion:nil];
}
Create an NSDateComponents object with the date difference you want to add, and add it to pickerDate via NSCalendar -dateByAddingComponents:toDate:options. Then create your notification based on the resulting date.
In this case, something like this:
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
[offsetComponents setDay:3];
NSDate *reminderDate = [gregorian dateByAddingComponents:offsetComponents toDate:pickerDate options:0];
Repeat for 7th, 14th, and 21st day.
This should be simple, but it's proving challenging for me. I'd like to know the best approach to calculating the difference in seconds between [NSDate date] and a future event x seconds from that time. There are several different types of event, and each event may occur several times a day, and at different times, depending what day of the week it happens to be.
What I am trying to do is have the user select an event type from a picker and then set an alarm in Notification Center for the next occurrence of that event based on their selection. I have everything working fine, except for the seconds calculation.
So, for example, let's say it's 9am on a Monday. I'd like to determine how many seconds it would be between now and a user selected event that regularly occurs every Tuesday, Thursday, and Saturday at 10am, 4pm, and 11pm on each day, or on Sunday at 1pm. How would you approach this most efficiently?
When you're talking about a time or date like "next Thursday at 1 PM", that's information that only makes sense in the context of a calendar. NSDate is not going to provide you with much help. It would perhaps be more appropriately named NSPointInTime. It's just a number of seconds that have passed from some earlier, arbitrary reference point in time. It has no notion of weekdays, ante/post meridiem, or even hour of the day.
The two objects that do know about those sorts of thing are NSDateComponents and NSCalendar. Working together, they can create an NSDate from a specification like "next Thursday at 1PM".
You can decompose any date into components using -[NSCalendar components:fromDate:], and you can then use other NSDateComponents objects to perform arithmetic on the individual pieces of information. Find the weekday of today, for example, and its difference from Thursday. Then use -[NSCalendar dateByAddingComponents:toDate:options:] to create a new date based on that offset.
#interface NSCalendar (NextWeekday)
- (NSInteger)maxWeekday;
- (NSDate *)dateFromComponents:(NSDateComponents *)comps
forNextWeekday:(NSInteger)weekday
atHour:(NSInteger)hour;
#end
#implementation NSCalendar (NextWeekday)
- (NSInteger)maxWeekday
{
return [self maximumRangeOfUnit:NSWeekdayCalendarUnit].length;
}
- (NSDate *)dateFromComponents:(NSDateComponents *)comps
forNextWeekday:(NSInteger)weekday
atHour:(NSInteger)hour
{
NSInteger diff = weekday - [comps weekday];
if( diff < 0 ){
diff += [self maxWeekday];
}
NSDateComponents * weekdayOffset = [NSDateComponents new];
[weekdayOffset setWeekday:diff];
[comps setHour:hour];
return [self dateByAddingComponents:weekdayOffset
toDate:[self dateFromComponents:comps]
options:0];
}
#end
#define GREGORIAN_THURSDAY 5
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSCalendar * cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents * wednesday = [NSDateComponents new];
[wednesday setDay:3];
[wednesday setWeekday:4];
[wednesday setMonth:6];
[wednesday setYear:2013];
NSDateComponents * friday = [NSDateComponents new];
[friday setDay:5];
[friday setWeekday:6];
[friday setMonth:6];
[friday setYear:2013];
NSDateComponents * now = [cal components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit|NSWeekdayCalendarUnit
fromDate:[NSDate date]];
NSDateComponents * lastSatOfDecember = [NSDateComponents new];
[lastSatOfDecember setDay:29];
[lastSatOfDecember setWeekday:7];
[lastSatOfDecember setMonth:12];
[lastSatOfDecember setYear:2012];
NSLog(#"From Wednesday: %#", [cal dateFromComponents:wednesday
forNextWeekday:GREGORIAN_THURSDAY
atHour:13]);
NSLog(#"From Friday: %#", [cal dateFromComponents:friday
forNextWeekday:GREGORIAN_THURSDAY
atHour:13]);
NSLog(#"From now: %#", [cal dateFromComponents:now
forNextWeekday:GREGORIAN_THURSDAY
atHour:13]);
NSLog(#"Crossing over the year: %#", [cal dateFromComponents:lastSatOfDecember
forNextWeekday:GREGORIAN_THURSDAY
atHour:13]);
}
return 0;
}
I'm current piecing together a streaming radio app for a show I work on and so far, it's okay - the streaming works once you push the 'Listen Live!' button and since that's the main aim, I'm happy. However, I'm trying to get clever now and set up an on-screen display that shows when the show is on the air; it's only on for two hours a week, so I thought it'd be nice to show when it's on and off via an on-screen display in the app. Nothing fancy... here's what I've got on screen so far:
1) A counting clock taken from here - EDIT: http://www.youtube.com/watch?v=pNVWST15pyc – that's really simple. Can't believe I didn't realise that changing the hh to HH makes it 24-hour... god, I'm so dumb.
2) A label to show just the day of the week, not the date or month, taken from here - NSCalendar to Display Weekday - as the app only needs to know whether it's Sunday (the on-air day) or not. EDIT: Made this work properly now because I'm an idiot who didn't link it up properly. :(
What I really want to do, however, is have the app set up two settings for an image view - an 'on air' and 'off air' switch - so that when it's between 8pm and 10pm on Sunday night, it shows the 'on air' image and when it's any other time, it shows the 'off air' one. I'm pretty sure that's an if statement but I'm not sure where to start trying to combine the clock and weekday bits to make that work. Can anyone make some suggestions please?
Also, since those times are GMT, I want to lock the app into GMT regardless of where in the world the user is so it relates directly to the show. I'm guessing I can do that using the timeZone:nil bit of the clock code by changing the 'nil' bit to 'Europe/London', but doing so just makes the whole thing crash out in spectacular fashion (I've tried it in various forms with no success). Again, suggestions would be massively appreciated.
Apologies for asking what may seem like simple questions - aside from some adult learning courses on Xcode, I'm a bit of a novice. :D
You should use the NSDateComponents object, which has a -weekday instance method (1 being Sunday for the gregorian calendar). Details on how to get started are in Apple's Date and Time Programming Guide. Here's a code sample that relates to what you are trying to do:
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];
NSDateComponents will also let you get and set (through so-called accessor methods) hour, minute, second, and timezone.
For the problem you described above, I would write a method like this:
- (BOOL)isShowOnAir {
BOOL onAir = NO;
NSDate *now = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [gregorian components:(NSWeekdayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSTimeZoneCalendarUnit) fromDate:now];
[components setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
NSInteger day = [components day]; // Sunday == 1
if (day == 1) {
NSInteger hour = [components hour];
//NSInteger minute = [components minute]; -- not used but here's how to access it
if (hour == 20 || hour == 21) { // covers 8:00 - 9:59 PM
onAir = YES;
}
}
return onAir;
}
Is there a better way to do this?
-(NSDate *)getMidnightTommorow {
NSCalendarDate *now = [NSCalendarDate date];
NSCalendarDate *tomorrow = [now dateByAddingYears:0 months:0 days:1 hours:0 minutes:0 seconds:0];
return [NSCalendarDate dateWithYear:[tomorrow yearOfCommonEra]
month:[tomorrow monthOfYear]
day:[tomorrow dayOfMonth]
hour:0
minute:0
second:0
timeZone:[tomorrow timeZone]];
}
Note that I always want the next midnight, even if it happens to be midnight when I make that call, however if it happens to be 23:59:59, I of course want the midnight that is coming in one second.
The natural language functions seem flaky, and I'm not sure what Cocoa would do if I pass 32 in the "day" field. (If that'd work I could drop the [now dateByAddingYears:...] call)
From the documentation:
Use of NSCalendarDate strongly
discouraged. It is not deprecated yet,
however it may be in the next major OS
release after Mac OS X v10.5. For
calendrical calculations, you should
use suitable combinations of
NSCalendar, NSDate, and
NSDateComponents, as described in
Calendars in Dates and Times
Programming Topics for Cocoa.
Following that advice:
NSDate *today = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [[NSDateComponents alloc] init];
components.day = 1;
NSDate *tomorrow = [gregorian dateByAddingComponents:components toDate:today options:0];
[components release];
NSUInteger unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
components = [gregorian components:unitFlags fromDate:tomorrow];
components.hour = 0;
components.minute = 0;
NSDate *tomorrowMidnight = [gregorian dateFromComponents:components];
[gregorian release];
[components release];
(I'm not sure offhand if this is the most efficient implementation, but it should serve as a pointer in the right direction.)
Note: In theory you can reduce the amount of code here by allowing a date components object with values greater than the range of normal values for the component (e.g. simply adding 1 to the day component, which might result in its having a value of 32). However, although dateFromComponents: may tolerate out-of-bounds values, it's not guaranteed to. You're strongly encouraged not to rely on it.
Nope - it'll be the same way you use to find midnight today.
NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:(24 * 60 * 60)];
NSDateComponents *components = [gregorian components:(NSYearCalendarUnit |
NSMonthCalendarUnit |
NSDayCalendarUnit)
fromDate:tomorrow];
NSDate *midnight = [gregorian dateFromComponents:components];
[NSDate dateWithNaturalLanguageString:#"midnight tomorrow"];
Convert your current date and time to a Unix date (seconds since 1970) or DOS style (since 1980), then add 24 hours and convert it back. Then reset the hours, minutes and seconds to zero to get to midnight.
You could try this way:
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setDay:1];
NSDate *tomorrow = [calendar dateByAddingComponents:comps toDate:[NSDate date] options:0]; //it gives us tomorrow with current time
NSDate *midnight = [calendar startOfDayForDate:tomorrow]; //here we get next midnight
It is also easy to retrieve the seconds interval if needed to set up an NSTimer:
double intervalToMidnight = midnight.timeIntervalSinceNow;