Question

I need to be able to calculate the time difference between two dates and then store that value in one digit precision decimal format. So if the time difference is 6 minutes then I need .1 to be returned, if it is 3 minutes I still need .1 returned, but if it is 7 minutes or 12 minutes, I need .2 to be returned. The subtraction of the time difference is working correctly:

NSTimeInterval interval = [currentFlight.landtime timeIntervalSinceDate:currentFlight.takeofftime];

That returns as expected so if the difference is 6 (minutes), the value I get back is 0.100000.

I also need to display this value to the user in a UILabel. When I use this number formatter, 0.100000 gets displayed as .2 instead of .1:

NSNumberFormatter *ftDecimalFormatter = [[NSNumberFormatter alloc] init];
[ftDecimalFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
[ftDecimalFormatter setMaximumFractionDigits:1];
[ftDecimalFormatter setMinimumFractionDigits:1];
[ftDecimalFormatter setRoundingMode:NSNumberFormatterRoundUp];

I have tried all the difference rounding methods, but none seem to work. Any suggestions?

Answer 1

Multiply the number by 10, add 0.9999999999999, truncate the fractional part (ie floor), then divide by 10. [You can achieve the same result other ways this is just one way.] Then you can just print your number with a format string specifying one decimal digit, no?