NSComparisonResult is not working as expected for 10 PM and above

Question

I need to compare two times in Swift and using NSComparisonResult I could get correct result until it comes to time between 10 PM - 11:59 PM. It shows opposite result for these times. Anyone know what's the issue with this? Below is sample code and scenario's. 10:30:00 PM is example time to test, but you can test it with any time.

// For test, Current time 10:30:00 PM
let currentTime = NSDateFormatter.localizedStringFromDate(NSDate(), dateStyle: .NoStyle, timeStyle: .LongStyle)

let closeTimeCompareResult: NSComparisonResult = currentTime.compare("10:00:00 PM EDT")
print("DinnerClose: \(closeTimeCompareResult.rawValue)")
// Expected result is -1 but, getting as 1

// It works perfect until 9:59:59 PM
let closeTimeCompareResult9: NSComparisonResult = currentTime.compare("9:00:00 PM EDT")
print("DinnerClose: \(closeTimeCompareResult9.rawValue)")
// As expected result is -1

You compare *strings* and not dates ... – Martin R Mar 25 '16 at 02:33 — Martin R, Mar 25 '16 at 02:33

score 2 · Accepted Answer · answered Mar 25 '16 at 02:39

You're performing a string comparison. So you're comparing these two strings, for example:

10:00:00 PM EDT
9:00:00 PM EDT

A string comparison compares the corresponding characters of each string, starting with the first character of each. The first character of "10:00:00 PM EDT" is "1" and the first character of "9:00:00 PM EDT" is "9". In Unicode and ASCII, "9" is code point 57 and "1" is code point 49. Since 57 > 49, "9" > "1", and "9:00:00 PM EDT" > "10:00:00 PM EDT".

You probably want to extract the hour, minute, and second from the input date, and then compare them numerically. If you've upgraded to Xcode 7.3 with Swift 2.2, then you can use a tuple comparison like this:

let date = NSDate()
let components = NSCalendar.currentCalendar().components([.Hour, .Minute, .Second], fromDate: date)
let hms = (components.hour, components.minute, components.second)
if hms >= (21, 0, 0) && hms < (22, 30, 0) {
    print("\(date) is between 9 PM and 10:30 PM in the system's time zone.")
}

Thanks, yes, I was comparing strings. Let me try with this approach. — Pandurang Yachwad, Mar 25 '16 at 02:41

NSComparisonResult is not working as expected for 10 PM and above

1 Answers1