无法在if语句中比较NSDates

Question

I am fetching data from iCloud and would like to compare it if it's more recent than the data on the device. However, my if statement evaluates to true even if the iCloud data is older.

Here is my code:

NSLog(@"users date: %@",userDefaultsModificationDate);
NSLog(@"icloud fetch date : %@",fetchedRemindersRecord.modificationDate);

NSComparisonResult result =  [[NSCalendar currentCalendar] compareDate:fetchedRemindersRecord.modificationDate toDate:userDefaultsModificationDate toUnitGranularity:NSCalendarUnitSecond];

    switch (result) {
        case NSOrderedSame:
            NSLog(@"same");
            break;

            case NSOrderedDescending:
            NSLog(@"desc");
            break;

            case NSOrderedAscending:
            NSLog(@"asc");
            break;

        default:
            break;
    }
if (result == NSOrderedDescending){

            [self createReminders:[NSKeyedUnarchiver unarchiveObjectWithData:[fetchedRemindersRecord objectForKey:@"reminders"]]];

            NSLog(@"Fetched records successfully users date: %@",userDefaultsModificationDate);
            NSLog(@"Fetched records successfully icloud fetch date : %@",fetchedRemindersRecord.modificationDate);
        }

Console:

users date: 2016-08-28 22:52:05 +0000
icloud fetch date : 2016-08-28 22:51:57 +0000
asc
Fetched records successfully users date: 2016-08-28 22:44:16 +0000
Fetched records successfully icloud fetch date : 2016-08-28 22:43:38 +0000

As you can see clearly, iCloud data is older, and the switch statement says that the order is ascending, however the if statement still evaluates to true. I even checked to make sure that both dates are not nil before comparing.

I have been struggling with this for an hour, can't seem to figure out what's going on.. probably some obvious thing which I am overlooking.

Thanks in advance!

EDIT : No matter what I compare result with, it always evalutes to true

Answer 1

When I run this code:

NSDateFormatter* df = [NSDateFormatter new];
df.dateFormat = @"yyyy-MM-dd HH:mm:ss";
NSDate* date1 = [df dateFromString:@"2016-08-28 22:52:05"];
NSDate* date2 = [df dateFromString:@"2016-08-28 22:51:57"];

NSLog(@"users date: %@", date1);
NSLog(@"icloud fetch date : %@", date2);

NSComparisonResult result =  [[NSCalendar currentCalendar] compareDate:date2 toDate:date1 toUnitGranularity:NSCalendarUnitSecond];

switch (result) {
    case NSOrderedSame:
        NSLog(@"same");
        break;

    case NSOrderedDescending:
        NSLog(@"desc");
        break;

    case NSOrderedAscending:
        NSLog(@"asc");
        break;

    default:
        break;
}
if (result == NSOrderedSame){
    NSLog(@"same 2");
}
if (result == NSOrderedDescending){
    NSLog(@"desc 2");
}
if (result == NSOrderedAscending){
    NSLog(@"asc 2");
}

I get this result:

2016-08-29 09:25:22.737 Junk6[34957:1961720] users date: 2016-08-28 12:52:05 +0000
2016-08-29 09:25:22.738 Junk6[34957:1961720] icloud fetch date : 2016-08-28 12:51:57 +0000
2016-08-29 09:25:22.738 Junk6[34957:1961720] asc
2016-08-29 09:25:22.739 Junk6[34957:1961720] asc 2

I can't run your code unless you post either the whole project, or a cut-down example which demonstrates the problem.