iPHONE SDK - Subtracting a time given another time

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iPHONE SDK - Subtracting a time given another time

Hi guys, having trouble with this. i need to come up with a logic code.

How do i, given 2 set of times. subtract one from the other and change it all to seconds.

Lets say i have '12:00:00' and '15:00:00' Now i want to subtract 12:00:00 from 15:00:00 so the result will be 03:00:00. Then change it all to seconds so that will be 10800 seconds

i already have two sets of time in an NSString after being Formatted with a NSDateFormatter

+2 A:

This is what you need to look for : NSDate -(NSTimeInterval)timeIntervalSinceDate

Convert your string to an NSDate and call this method [thisDate timeIntervalSinceDate:thatDate] will return you an NSTimeInterval, type double

vodkhang 2010-06-24 06:49:55

hi . thx for replying. I need some help with converting the NSString to an NSDate. could u share some sample code?

Kenneth 2010-06-24 07:07:01

ah ok nvm i found the dateFromString:String method

Kenneth 2010-06-24 07:10:46

ah i have another problem, how do i assign it to a variable? sorry for asking but im new to obj-c

Kenneth 2010-06-24 07:19:05

What is "it"? You mean the NSTimeInterval? It is not an object, you have to use NSTimeInterval time = [thisDate timeIntervalSinceDate:thatDate]; or you can use double. But I prefer NSTimeInterval

vodkhang 2010-06-24 07:25:20

im getting null or 0 when NSLogged. here is the code that im using

Kenneth 2010-06-24 07:33:21

NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init]; [dateFormat setDateFormat:@"dd/MM/yyyy"]; NSDateFormatter *timeFormat = [[NSDateFormatter alloc] init]; [timeFormat setDateFormat:@"HH:mm:ss"]; NSDate *now = [[NSDate alloc] initWithTimeIntervalSinceNow:-3*60*60];NSDate *now2 = [[NSDate alloc] init];

Kenneth 2010-06-24 07:33:39

NSString *theTime = [timeFormat stringFromDate:now]; NSString *theTimeNOW = [timeFormat stringFromDate:now2]; NSDate *cDate1 = [timeFormat dateFromString:theTime]; NSDate *cDate2 = [timeFormat dateFromString:theTimeNOW]; NSTimeInterval time = [cDate2 timeIntervalSinceDate:cDate1]; NSLog(@"time IN COREPLOT VIEW ~~~CONTROLLER~~ %@",time);

Kenneth 2010-06-24 07:34:48

No, it is not an object, for sure, use %f for double. I mean this line : NSLog(@"time IN COREPLOT VIEW ~~~CONTROLLER~~ %@",time);

vodkhang 2010-06-24 07:40:35

And then, why do you need to convert to NSString just to convert back to NSDate?

vodkhang 2010-06-24 07:41:27

oh cool. alright . Thanks . got it working now.

Kenneth 2010-06-24 07:42:53

oh yeah . good point. haha , guess i was thinking too much about it that i didn't noticed that.

Kenneth 2010-06-24 07:45:05

ansaurus

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iPHONE SDK - Subtracting a time given another time

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