How do I implement previous/next month buttons and show dates for current month?

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 controll

Answer 1

Here are some methods that should do what you want:

First, in your viewDidLoad method add:

self.startDate = [NSDate date];
[self updateDateRange];

This gives you a starting point. Then, I added the following five methods (Note: previousMonthButtonPressed/nextMonthButtonPressed should be wired up to your buttons):

// Return the first day of the month for the month that 'date' falls in:
- (NSDate *)firstDayOfMonthForDate:(NSDate *)date
{
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:date];
    comps.day               = 1;
    return [cal dateFromComponents:comps];
}

// Return the last day of the month for the month that 'date' falls in:
- (NSDate *)lastDayOfMonthForDate:(NSDate *)date
{
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:date];
    comps.month             += 1;
    comps.day               = 0;
    return [cal dateFromComponents:comps];
}

// Move the start date back one month
- (IBAction)previousMonthButtonPressed:(id)sender {
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:self.startDate];
    comps.month             -= 1;
    self.startDate          = [cal dateFromComponents:comps];
    [self updateDateRange];
}

// Move the start date forward one month
- (IBAction)nextMonthButtonPressed:(id)sender {
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:self.startDate];
    comps.month             += 1;
    self.startDate          = [cal dateFromComponents:comps];
    [self updateDateRange];
}

// Print the new range of dates.
- (void)updateDateRange
{
    NSLog(@"First day of month: %@", [self firstDayOfMonthForDate:self.startDate]);
    NSLog(@"Last day of month: %@",  [self lastDayOfMonthForDate:self.startDate]);
}