Display dates for a year in a tableview - arrays

Question

What I am trying to accomplish here is taking a tableView with a prototype cell, and display the dates in each cell for a year, or two years. I have gotten it to display todays date in the label by using the following code:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"MM/dd/yyyy"];
NSDate *dateNow = [NSDate date];
dateArray = [NSMutableArray arrayWithObjects:[dateFormatter stringFromDate:dateNow], nil];
It works to add one date (todays date) to the first cell. I can not figure out how to get it to add all days by an interval of 1. Any help?
I display the information in the array with this code:
static NSString *CellIdentifier = #"Cell";
Custom *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
cell.dateLabel.text = [dateArray objectAtIndex:indexPath.row];

Answer 1

Here you go,
in the viewDidload,
dateArray = [[NSMutableArray alloc] init]; //dateArray is global
NSDate *thisDate, *nextDate;
thisDate = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"MM/dd/yyyy"];
[dateArray addObject: [dateFormatter stringFromDate:thisDate]];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [[NSDateComponents alloc] init];
components.day = 1;
for (int i = 0; i<365; i++) //Not considering leap years
{
nextDate = [gregorian dateByAddingComponents:components toDate:thisDate options:0];
[dateArray addObject:[dateFormatter stringFromDate:nextDate]];
thisDate = nextDate;
}
in the cellForRowAtIndexPath
cell.dateLabel.text = [dateArray objectAtIndex:indexPath.row];

Answer 2

You don't need to maintain an array of dates. If you want to display the nth row, you can just add n days to your start date and use that.
So you'd have your start date stored in an instance variable:
NSDate *_startDate;
To determine how many rows should be in the tableView, you have to figure out how many days are in that year (I'm going to assume you're only displaying one year):
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// get the calendar
NSCalendar *calendar = [NSCalendar currentCalendar];
// get the date that points to the first day of the first month of the year containing the start date
// note that we include the era, because some calendars have more than an "AD"/"BC" kind of era
NSDateComponents *yearStartComponents = [calendar components:(NSEraCalendarUnit | NSYearCalendarUnit) fromDate:_startDate];
[yearStartComponents setMonth:1];
[yearStartComponents setDay:1];
NSDate *startOfYear = [calendar dateFromComponents:yearStartComponents];
NSDateComponents *yearDiff = [[NSDateComponents alloc] init];
[yearDiff setYear:1];
// add one year to that date
NSDate *startOfNextYear = [calendar dateByAddingComponents:yearDiff toDate:startOfYear options:0];
// figure out how many days were between the two dates
NSDateComponents *dayDiff = [calendar components:NSDayCalendarUnit fromDate:startOfYear toDate:startOfNextYear options:0];
return [dayDiff day];
}
And then when you need the cell, you can just use the "row" of the indexPath as the number of days from the start date:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = ...;
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *diff = [[NSDateComponents alloc] init];
[diff setDay:[indexPath row]];
NSDate *date = [calendar dateByAddingComponents:diff toDate:_startDate options:0];
NSLocale *locale = [NSLocale currentLocale];
NSString *formatted = [NSDateFormatter localizedStringFromDate:date dateStyle:NSDateFormatterShortStyle timeStyle:NSDateFormatterNoStyle locale:locale];
[[cell textLabel] setText:formatted];
return cell;
}
There are several nice things about this approach:
It works regardless of the length of the year. Whether the current year has 353, 355, 365, 366, or 384 days in the year, it'll work.
It works regardless of the current calendar. There's more than just the Gregorian calendar out there. NSCalendar supports the Gregorian, Buddhist, Chinese, Hebrew, Islamic, Islamic Civil, Japanese, Republic of China, Persian, Indian, and ISO8601 calendars.
You're not hard-coding a format string. By using the NSDateFormatterStyles, you'll be using the appropriate short-hand notation for a date, whether that's "5/12/12" or "5 Dec '12" or something entirely different.