UIDatePicker odd behavior when setting minuteInterval

http://stackoverflow.com/questions/6948297/uidatepicker-odd-behavior-when-setting-minuteinterval

Here's yet another approach, with an Objective-C category!

I took the spirit of @zurbergram's rounding behavior (up/down to closest) and @mmorris's overall answer and came up with this category:

#import <UIKit/UIKit.h>

@interface UIDatePicker (SetDateRounded)

-(void)setMinimumDateRoundedByMinuteInterval:(NSDate *)minimumDate;
-(void)setDateRoundedByMinuteInterval:(NSDate *)date animated:(BOOL)animatedYesNo;

@end

@implementation UIDatePicker (SetDateRounded)

-(void)setDateRoundedByMinuteInterval:(NSDate *)date animated:(BOOL)animatedYesNo
{
    NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSMinuteCalendarUnit fromDate:date];
    NSInteger minutes = [dateComponents minute];
    NSInteger minutesRounded = roundf((float)minutes / (float)[self minuteInterval]) * self.minuteInterval;
    NSDate *roundedDate = [[NSDate alloc] initWithTimeInterval:60.0 * (minutesRounded - minutes) sinceDate:date];
    [self setDate:roundedDate animated:animatedYesNo];
}

-(void)setMinimumDateRoundedByMinuteInterval:(NSDate *)date
{
    NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSMinuteCalendarUnit fromDate:date];
    NSInteger minutes = [dateComponents minute];
    NSInteger minutesRounded = roundf((float)minutes / (float)[self minuteInterval]) * self.minuteInterval;
    NSDate *roundedDate = [[NSDate alloc] initWithTimeInterval:60.0 * (minutesRounded - minutes) sinceDate:date];
    [self setMinimumDate:roundedDate];
}

@end

Then in your implementation, you can do something like this:

#import "UIDatePicker+SetDateRounded.h"

...

- (void)viewDidLoad
{
    [super viewDidLoad];

    _datePicker.minuteInterval = 15;

    [_datePicker setMinimumDateRoundedByMinuteInterval:[NSDate date]];
    [_datePicker setDateRoundedByMinuteInterval:[NSDate date] animated:YES];
}