How to compare two time from NSDate. Returning nil for nsdate when doing comparision. #debug my code

问题

Here is the code:

// get current date/time
    NSDate *today = [NSDate date];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    // display in 12HR/24HR (i.e. 11:25PM or 23:25) format according to User Settings
    [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
    [dateFormatter setDateFormat:@"HH:mm:ss"];
    NSString *currentTime = [dateFormatter stringFromDate:today];
    currentTime = [currentTime stringByReplacingOccurrencesOfString:@"AM" withString:@""];
    currentTime = [currentTime stringByReplacingOccurrencesOfString:@"PM" withString:@""];
    currentTime = [currentTime stringByReplacingOccurrencesOfString:@" " withString:@""];

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setTimeStyle:NSDateFormatterMediumStyle];
    [formatter setDateFormat:@"HH:mm:ss"];

    NSDate *date1= [formatter dateFromString:currentTime];
    NSDate *date2 = [formatter dateFromString:@"5:00:00"];


    NSComparisonResult result = [date1 compare:date2];
    if(result == NSOrderedDescending)
    {
        NSLog(@"date1 is later than date2"); 
    }

Here when I run the code I am getting date1 and date2 as nil, while I am properly getting the current time in 24 hour format. I had applied same date formatting while getting current time from [NSDate date] . What am I missing here?

EDIT 1: Fixed the typo and changed the title.

EDIT 2: As per suggestion, To compare Only the hour I can use:

NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *components = [calendar components:(NSHourCalendarUnit) fromDate:date1];

    NSInteger hour = [components hour];

EDIT 3: Changed the title, to match the exact requirements.

But I am not able to retrieve date1 from current time. It throws a garbage value .

回答1:

There was a typo:
[dateFormatter setDateFormat:@"HH:mm:ss"];
should be:
[formatter setDateFormat:@"HH:mm:ss"];

To compare two dates use:

NSDate *date1 = [NSDate date];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"HH:mm:ss"];
NSDate *date2 = [formatter dateFromString:@"05:00:00"];

NSComparisonResult result = [date1 compare:date2];
if(result == NSOrderedDescending)
{
    NSLog(@"date1 is later than date2");
}

If you only want to compare the hours:

NSCalendar *calendar = [NSCalendar currentCalendar];

NSDate *date1 = [NSDate date];
NSDateComponents *date1Components = [calendar components:NSCalendarUnitHour fromDate:date1];
NSInteger date1Hour = date1Components.hour;

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"HH:mm:ss"];
NSDate *date2 = [formatter dateFromString:@"05:00:00"];
NSDateComponents *date2Components = [calendar components:NSCalendarUnitHour fromDate:date2];
NSInteger date2Hour = date2Components.hour;

if(date1Hour > date2Hour) {
    NSLog(@"date1 is later than date2");
}

来源：https://stackoverflow.com/questions/25571399/how-to-compare-two-time-from-nsdate-returning-nil-for-nsdate-when-doing-compari

标签

ios

objective-c

datetime

nsdate

nsdateformatter