Display NSDates in terms of week

Question

Scenario:

I have an expense tracking iOS Application and I am storing expenses from a expense detail view controller into a table view (with fetched results controller) that shows the list of expenses along with the category and amount and date. I do have a date attribute in my entity "Money" which is a parent entity for either an expense or an income.

Question:

What I want is to basically categorize my expenses for a given week, a month, or year and display it as the section header title for example : (Oct 1- Oct 7, 2012) and it shows expenses amount and related stuff according to that particular week. Two buttons are provided in that view, if I would press the right button, it will increment the week by a week (Oct 1- Oct 7, 2012 now shows Oct8 - Oct 15, 2012) and similarly the left button would decrement the week by a week.

How would I accomplish that? I am trying the following code - doesn't work.

- (void)weekCalculation
{
   NSDate *today = [NSDate date];  // present date (current date)

   NSCalendar* calendar = [NSCalendar currentCalendar];
   NSDateComponents* comps = [calendar components:NSYearForWeekOfYearCalendarUnit |NSYearCalendarUnit|NSMonthCalendarUnit|NSWeekCalendarUnit|NSWeekdayCalendarUnit fromDate:today];

   [comps setWeekday:1]; // 1: Sunday
   firstDateOfTheWeek = [[calendar dateFromComponents:comps] retain];
   [comps setWeekday:7]; // 7: Saturday
   lastDateOfTheWeek = [[calendar dateFromComponents:comps] retain];

   NSLog(@" first date of week =%@", firstDateOfTheWeek);
   NSLog(@" last date of week =%@", lastDateOfTheWeek);

   firstDateOfWeek = [dateFormatter stringFromDate:firstDateOfTheWeek];
   lastDateOfWeek = [dateFormatter stringFromDate:lastDateOfTheWeek];

}

Code for incrementing date -

- (IBAction)showNextDates:(id)sender
{
   int addDaysCount = 7;

   NSDateComponents *dateComponents = [[[NSDateComponents alloc] init] autorelease];
   [dateComponents setDay:addDaysCount];

   NSDate *newDate1 = [[NSCalendar currentCalendar]
                    dateByAddingComponents:dateComponents
                    toDate:firstDateOfTheWeek options:0];

   NSDate *newDate2 = [[NSCalendar currentCalendar]
                    dateByAddingComponents:dateComponents
                    toDate:lastDateOfTheWeek options:0];

   NSLog(@" new dates =%@ %@", newDate1, newDate2);

}

Suppose the week shows like this (Nov4, 2012 - Nov10, 2012) and I press the increment button, I see in the console, date changes to Nov11,2012 and Nov.17, 2012 which is right but if I press the increment button again, it shows the same date again (Nov 11, 2012 and Nov.17, 2012).

Please help me out here.

Your firstDateOfWeek and lastDateOfWeek are string and not dates. When you are using in [[NSCalendar currentCalendar] dateByAddingComponents:dateComponents toDate:firstDateOfTheWeek options:0];, you need to convert to dates. — iDev, Nov 09 '12 at 08:06
@ACB you read it wrong. They are dates only. Read it carefully Sir. — Angad Manchanda, Nov 09 '12 at 08:07
@ACB Do you think this code should increment the date by a week, no matter how many times the increment button is pressed ? — Angad Manchanda, Nov 09 '12 at 08:08
Oh okay. firstDateOfWeek and lastDateOfTheWeek looks confusing. In that case can you print lastDateOfTheWeek and check what is the date before incrementing again? — iDev, Nov 09 '12 at 08:09
NSDate *today = [NSDate date]; // present date (current date) NSDateComponents* comps = [calendar components:NSYear..Unit fromDate:today]; So it will always calculate from today's week right? if I am correct you should switch to new date here itself. — iDev, Nov 09 '12 at 08:11
@ACB I print them and it shows that lastDateOfTheWeek is Nov.10, 2012 and when I increment, the date becomes 17 Nov 2012. I press the increment button again and it prints the same results. Does the above code looks right to you? — Angad Manchanda, Nov 09 '12 at 08:13
@ACB You make sense. Please post the right code. Thanks man. — Angad Manchanda, Nov 09 '12 at 08:14
@ACB Shouldn't I include 2 date properties because I have two dates, right. self.currentDate = newDate1; I would probably need to add another date variable, right? — Angad Manchanda, Nov 09 '12 at 08:23
No, basically all you need to know is the sunday corresponding to the given date. So you can use any of them to get that. When you are incrementing by 7 days, sunday of this week becomes sunday of next week. So you will ideally get the same day as sunday from week calculation and then when you calculate it will add 7 more days to that get its next week. Since you already got sunday, saturday of that week also will be automatically calculated by week calculation method. Try it out. — iDev, Nov 09 '12 at 08:26

score 2 · Accepted Answer · answered Nov 09 '12 at 08:15

2

Declare currentDate as an @property in your class. And try this.

@property(nonatomic, retain) NSDate *currentDate;

Initially set

self.currentDate = [NSDate date];

before calling this method.

- (void)weekCalculation
{
   NSCalendar* calendar = [NSCalendar currentCalendar];
   NSDateComponents* comps = [calendar components:NSYearForWeekOfYearCalendarUnit |NSYearCalendarUnit|NSMonthCalendarUnit|NSWeekCalendarUnit|NSWeekdayCalendarUnit fromDate:self.currentDate];

   [comps setWeekday:1]; // 1: Sunday
   firstDateOfTheWeek = [[calendar dateFromComponents:comps] retain];
   [comps setWeekday:7]; // 7: Saturday
   lastDateOfTheWeek = [[calendar dateFromComponents:comps] retain];

   NSLog(@" first date of week =%@", firstDateOfTheWeek);
   NSLog(@" last date of week =%@", lastDateOfTheWeek);

   firstDateOfWeek = [dateFormatter stringFromDate:firstDateOfTheWeek];
   lastDateOfWeek = [dateFormatter stringFromDate:lastDateOfTheWeek];

}

Once the view is loaded self.currentDate value should be updated from showNextDates. Make sure it is not getting reset anywhere else.

- (IBAction)showNextDates:(id)sender
{
   int addDaysCount = 7;

   NSDateComponents *dateComponents = [[[NSDateComponents alloc] init] autorelease];
   [dateComponents setDay:addDaysCount];

   NSDate *newDate1 = [[NSCalendar currentCalendar]
                    dateByAddingComponents:dateComponents
                    toDate:firstDateOfTheWeek options:0];

   NSDate *newDate2 = [[NSCalendar currentCalendar]
                    dateByAddingComponents:dateComponents
                    toDate:lastDateOfTheWeek options:0];

   NSLog(@" new dates =%@ %@", newDate1, newDate2);

   self.currentDate = newDate1;

}

answered Nov 09 '12 at 08:15

iDev

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No, this doesn't work. When I press the increment button, first time, the date changes to 11 nov 2012 - 17 nov 2012, that's right but when I again press the button second time, it displays the same date again. – Angad Manchanda Nov 09 '12 at 08:40
What is printing in NSLog of first date of week ? is there any chance that you are restting currentDate? Also try with self.currentDate = newDate2; – iDev Nov 09 '12 at 08:42
It doesn't work at all. See this output: 2012-11-09 00:48:58.650 XpenseTrack[52798:c07] first date of week =2012-11-04 07:00:00 +0000 2012-11-09 00:48:58.650 XpenseTrack[52798:c07] last date of week =2012-11-10 08:00:00 +0000 2012-11-09 00:49:03.678 XpenseTrack[52798:c07] self current date = 2012-11-11 08:00:00 +0000 2012-11-17 08:00:00 +0000 2012-11-09 00:49:06.206 XpenseTrack[52798:c07] self current date = 2012-11-11 08:00:00 +0000 2012-11-17 08:00:00 +0000 2012-11-09 00:49:08.972 XpenseTrack[52798:c07] self current date = 2012-11-11 08:00:00 +0000 2012-11-17 08:00:00 +0000 – Angad Manchanda Nov 09 '12 at 08:49
It prints the same date over and over after pressing the increment button. – Angad Manchanda Nov 09 '12 at 08:49
Where is the NSLog for "new Dates = "? What are the two new dates after adding 7? Can you check while setting currentDate = newDate1, is it setting the next week's sunday there? – iDev Nov 09 '12 at 08:54
Those were the new dates only I printed.It seems to be confusing to me. – Angad Manchanda Nov 09 '12 at 08:58
there is another answer posted to this question, but while incrementing, it increments the date by 7, that's right. But I need to increment a week. – Angad Manchanda Nov 09 '12 at 09:00
I searched for that word and I cant locate it. Are you sure that you copy pasted exactly the same code in my answer? – iDev Nov 09 '12 at 09:01
I got it to work. I actually had to call [self weekCalculation] method inside these increment and decrement button actions. Now, it's working perfectly. – Angad Manchanda Nov 09 '12 at 09:06
@AngadManchanda, Yes you have to call that to update the get the new sunday and saturday. I thought that was already done. Anyways thanks for accepting. If it helped please click on the vote up(up arrow) as well. Actually I tried this code my self and I am getting it properly. – iDev Nov 09 '12 at 09:09
perfect. Please look into this last issue. You have been a great help so far. http://stackoverflow.com/questions/13302063/nsfetchedresultscontroller-with-section-names – Angad Manchanda Nov 09 '12 at 09:10

score 1 · Answer 2 · edited Nov 09 '12 at 08:32

I had needed similar thing in one of my old projects and achieved it via the code below. It sets this weeks date to an NSDate variable and adds/removes 7 days from day component in each button click. Here is the code:

NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];
NSDate *date = [NSDate date];
NSDateComponents *components = [calendar components:(NSYearCalendarUnit|NSWeekdayCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)  fromDate:date ];
//
[components setDay:([components day] - ([components weekday] )+2)];
self.currentDate = [calendar dateFromComponents:components];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = @"dd.MM.yyyy HH:mm:ss";
self.datelabel.text = [formatter stringFromDate:self.currentDate];

The code above calculates this week start and sets it to currentDate variable. I Have two UIButtons with UIActions named prevClick and nextClick which calls the method that sets the next or previous weekstart:

- (IBAction)prevClick:(id)sender {
[self addRemoveWeek:NO];

}

-(void)addRemoveWeek:(BOOL)add{
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];
NSDateComponents *components = [calendar components:(NSYearCalendarUnit|NSWeekdayCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)  fromDate:self.currentDate ];
components.day = add?components.day+7:components.day-7;
self.currentDate = [calendar dateFromComponents:components];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = @"dd.MM.yyyy HH:mm:ss";
self.datelabel.text = [formatter stringFromDate:self.currentDate];

}

- (IBAction)nextClk:(id)sender {
[self addRemoveWeek: YES];

}

@Alessandro The code which you wrote basically adds 7 days to the date when I press the increment button. What I want is that the increment button should increment my start date of the week and also the end date of the week by 7 days. like my label displays :(Oct 1, 2012 - Oct 7, 2012). After the increment button action, the label should display (Oct 8, 2012 - Oct 15, 2012). How would I accomplish that? — Angad Manchanda, Nov 09 '12 at 08:45
@madiden The code which you wrote basically adds 7 days to the date when I press the increment button. What I want is that the increment button should increment my start date of the week and also the end date of the week by 7 days. like my label displays :(Oct 1, 2012 - Oct 7, 2012). After the increment button action, the label should display (Oct 8, 2012 - Oct 15, 2012). How would I accomplish that? — Angad Manchanda, Nov 09 '12 at 08:50

Display NSDates in terms of week

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