Calculating hour difference iOS - ios

Question

I have written like this to calculate hour difference.
+ (NSInteger)hoursBetweenDate:(NSDate*)fromDateTime andDate:(NSDate *)toDateTime
{
NSDate *fromDate;
NSDate *toDate;
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
[calendar rangeOfUnit:NSHourCalendarUnit startDate:&fromDate
interval:NULL forDate:fromDateTime];
[calendar rangeOfUnit:NSHourCalendarUnit startDate:&toDate
interval:NULL forDate:toDateTime];
NSDateComponents *difference = [calendar components:NSHourCalendarUnit
fromDate:fromDate toDate:toDate options:0];
return [difference hour];
}
Problem is that if input is like this,
2016-03-09 07:58:39 +0000 (fromDateTime)
2016-03-09 09:07:44 +0000 (toDateTime),
difference is always 2 hours. Actually, it should be 1 hour and 10 minute. As a result, I only want to show 1 hour. Is there a way to round up or down?

Answer 1

If you are just interested in the "unformatted" number of hours between to dates, you can use NSTimeInterval and calculate it easily.
+(int)fullHoursBetweenDate:(NSDate *)date1 andDate:(NSDate *)date2 {
NSTimeInterval interval = [date2 timeIntervalSinceDate:date1];
return (int)interval / 3600;
}

Answer 2

You extracted out only the hour component (NSHourCalendarUnit) before you compare, that's why it's always 2 (9 - 7). Added NSMinuteCalendarUnit the result would be 1:
+ (NSInteger)hoursBetweenDate:(NSDate*)fromDateTime andDate:(NSDate *)toDateTime
{
NSDate *fromDate;
NSDate *toDate;
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
[calendar rangeOfUnit:NSHourCalendarUnit|NSMinuteCalendarUnit startDate:&fromDate
interval:NULL forDate:fromDateTime];
[calendar rangeOfUnit:NSHourCalendarUnit|NSMinuteCalendarUnit startDate:&toDate
interval:NULL forDate:toDateTime];
NSDateComponents *difference = [calendar components:NSHourCalendarUnit
fromDate:fromDate toDate:toDate options:0];
return [difference hour];
}
Also, if you are targeting iOS 8+, you should use NSCalendarUnitHour and NSCalendarUnitMinute instead as NSHourCalendarUnit and NSMinuteCalendarUnit were deprecated.

Answer 3

This small NSCalendar extension should do a trick for you.
extension NSCalendar {
func hoursBetweenDates(startDate: NSDate, endDate: NSDate) -> Int {
let days = differenceInDates(startDate, endDate: endDate, unit: .Hour)
return days
}
func differenceInDates(startDate: NSDate, endDate: NSDate, unit: NSCalendarUnit) -> Int {
let startUnit = ordinalityOfUnit(unit, inUnit: .Era, forDate:startDate)
let endUnit = ordinalityOfUnit(unit, inUnit: .Era, forDate:endDate)
let difference = endUnit-startUnit
return difference
}
}
And Obj-C version can be written as follow:
#interface NSCalendar (Duration)
-(NSNumber *)hoursBetweenStartDate:(NSDate*)startDate andEndDate:(NSDate*) endDate;
#end
#implementation NSCalendar (Duration)
-(NSNumber *)hoursBetweenStartDate:(NSDate*)startDate andEndDate:(NSDate*) endDate {
NSUInteger startUnit = [self ordinalityOfUnit:NSCalendarUnitHour inUnit:NSCalendarUnitEra forDate:startDate];
NSUInteger endUnit = [self ordinalityOfUnit:NSCalendarUnitHour inUnit:NSCalendarUnitEra forDate:endDate];
return [NSNumber numberWithUnsignedInteger: (endUnit - startUnit)];
}
#end

Answer 4

Modify this function as per your requirement
+(NSString*)timeDifference:(NSDate*)startDate endDate:(NSDate*)endDate{
NSDateComponents *components;
NSInteger days;
NSInteger hour;
NSInteger minutes;
NSString *strDuration;
components = [[NSCalendar currentCalendar] components: NSCalendarUnitDay|NSCalendarUnitHour|NSCalendarUnitMinute
fromDate: startDate toDate: endDate options: 0];
days = [components day];
hour=[components hour];
minutes=[components minute];
if(days>0){
if(days>1){
strDuration=[NSString stringWithFormat:#"%d days",days];
}
else{
strDuration=[NSString stringWithFormat:#"%d day",days];
}
return strDuration;
}
if(hour>0){
if(hour>1){
strDuration=[NSString stringWithFormat:#"%d hours",hour];
}
else{
strDuration=[NSString stringWithFormat:#"%d hour",hour];
}
return strDuration;
}
if(minutes>0){
if(minutes>1){
strDuration=[NSString stringWithFormat:#"%d minutes",minutes];
}
else{
strDuration=[NSString stringWithFormat:#"%d minute",minutes];
}
return strDuration;
}
return #"";
}