NSString+TimeCategory.h

//------------------------------------------------

#import <foundation foundation.h="">

@interface NSString (TimeCategory)

+ (NSString *)stringWithTime:(NSTimeInterval)time;

- (NSTimeInterval)timeValue;

@end

//------------------------------------------------

//NSString+TimeCategory.m

//------------------------------------------------

#import "NSString+TimeCategory.h"

@implementation NSString (TimeCategory)

+ (NSString *)stringWithTime:(NSTimeInterval)time {

    BOOL isPositive;

    NSInteger timeInt;

    if (time >  *  || time < -  * )

        return nil;

    if (time < ) {

        timeInt = (NSInteger)-time;

        isPositive = NO;

    } else {

        timeInt = (NSInteger)time;

        isPositive = YES;

    }

    NSInteger hour = timeInt/;

    NSInteger minute = (timeInt%)/;

    NSInteger second = (timeInt%)%;

    if (hour > ) {

        if (isPositive) {

            return [NSString stringWithFormat:@"%d%d:%d%d:%d%d",

hour/, hour%, minute/, minute%, second/, second%];

        } else {

            return [NSString stringWithFormat:@"-%d%d:%d%d:%d%d",

hour/, hour%, minute/, minute%, second/, second%];

        }

    } else {

        if (isPositive) {

            return [NSString stringWithFormat:@"%d%d:%d%d", minute/, minute%, second/, second%];

        } else {

            return [NSString stringWithFormat:@"-%d%d:%d%d", minute/, minute%, second/, second%];

        }

    }

}

- (NSTimeInterval)timeValue {

    NSInteger hour = , minute = , second = ;

    NSArray *sections = [self componentsSeparatedByString:@":"];

    NSInteger count = [sections count];

    second = [[sections objectAtIndex:count - ] integerValue];

    minute = [[sections objectAtIndex:count - ] integerValue];

    if (count > ) {

        hour = [[sections objectAtIndex:] integerValue];

    }

    return hour *  + minute *  + second;

}

@end

</foundation>