NSDate compare always returns NSOrderedSame - ios

Question

I have a problem with NSDate comparison. I tried out several solutions that I found while googling my problem but nothing changes: I compare two dates and I always get NSOrderedSame or difference between NSTimeIntervals = 0.0000;
My code looks like this:
NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
[inputFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
for (checklisteModel *updateRecord in updateArray)
{
NSDate *serverDate = [inputFormatter dateFromString:updateRecord.last_update];
NSString *lastUpdateFromLocalRecord = [self getLastUpdateForChecklisteItemWithID:updateRecord.checklisteID];
NSDate *localDate = [inputFormatter dateFromString:lastUpdateFromLocalRecord];
NSDateFormatter* fmt = [[NSDateFormatter alloc] init];
NSLog(#"checkliste ID: %i",updateRecord.checklisteID);
NSLog(#"server Date: ----- %#",[fmt stringFromDate:serverDate]);
NSLog(#"local Date: ----- %#",lastUpdateFromLocalRecord);
NSLog(#"difference of dates: %f",[serverDate timeIntervalSinceDate:localDate]);
NSTimeInterval distanceBetweenDates = [serverDate timeIntervalSinceDate:localDate];
double secondsInMinute = 60;
NSInteger secondsBetweenDates = distanceBetweenDates / secondsInMinute;
if (secondsBetweenDates == 0)
NSLog(#"seconds between == 0");
else if (secondsBetweenDates < 0)
NSLog(#"seconds between < 0");
else
NSLog(#"seconds between > 0");
//last_update on server is earlier than local
if ([serverDate compare:localDate] == NSOrderedAscending)
{
NSLog(#"Server data is earlier than local data");
NSLog([NSString stringWithFormat:#"server data: %#, local data: %#",updateRecord.last_update,lastUpdateFromLocalRecord]);
}
// server data is later than local data
else if ([serverDate compare:localDate] == NSOrderedDescending)
{
NSLog(#"Server data is later than local data");
NSLog([NSString stringWithFormat:#"server data: %#, local data: %#",updateRecord.last_update,lastUpdateFromLocalRecord]);
}
else
{
NSLog(#"Server data and local data are the same");
}
}
And part of my debugging shows this:
checkliste ID: 21
server Date: -----
local Date: ----- 2012-10-29 10:13:46
difference of dates: 3810.000000
seconds between > 0
Server data is later than local data
server data: 2012-10-29 11:17:16, local data: 2012-10-29 10:13:46

Answer 1

NSLog(#"server Date: ----- %#",updateRecord.last_update);
You're not logging serverDate here, so as Hot Licks suggested, there's a good chance that it's nil. You can send messages to nil in Objective-C, and the result is 0 or nil. What do you think the value of NSOrderedSame is? I'll bet a dollar that it's 0.
[inputFormatter setDateFormat:#"yyyy-MM-dd HH:mm"];
I notice that your date formatter's input format doesn't exactly match what you're logging, so maybe the difference between the expected input and what you're providing is enough to prevent the formatter from creating a date. Try adding seconds to the date format for inputFormatter.