conversion from NSTimeInterval to hour,minutes,seconds,milliseconds in swift

Swift 4, without using the `.remainder` (which returns wrong values):

func stringFromTimeInterval(interval: Double) -> NSString {

let hours = (Int(interval) / 3600)
let minutes = Int(interval / 60) - Int(hours * 60)
let seconds = Int(interval) - (Int(interval / 60) * 60)

return NSString(format: "%0.2d:%0.2d:%0.2d",hours,minutes,seconds)
}

Swift 3 solution for iOS 8+, macOS 10.10+ if the zero-padding of the hours doesn't matter:

func stringFromTime(interval: TimeInterval) -> String {
let ms = Int(interval.truncatingRemainder(dividingBy: 1) * 1000)
let formatter = DateComponentsFormatter()
formatter.allowedUnits = [.hour, .minute, .second]
return formatter.string(from: interval)! + ".\(ms)"
}

print(stringFromTime(interval: 12345.67)) // "3:25:45.670"

swift 3 version of @hixField answer, now with days and handling previous dates:

extension TimeInterval {
func timeIntervalAsString(_ format : String = "dd days, hh hours, mm minutes, ss seconds, sss ms") -> String {
var asInt = NSInteger(self)
let ago = (asInt < 0)
if (ago) {
asInt = -asInt
}
let ms = Int(self.truncatingRemainder(dividingBy: 1) * (ago ? -1000 : 1000))
let s = asInt % 60
let m = (asInt / 60) % 60
let h = ((asInt / 3600))%24
let d = (asInt / 86400)

var value = format
value = value.replacingOccurrences(of: "hh", with: String(format: "%0.2d", h))
value = value.replacingOccurrences(of: "mm", with: String(format: "%0.2d", m))
value = value.replacingOccurrences(of: "sss", with: String(format: "%0.3d", ms))
value = value.replacingOccurrences(of: "ss", with: String(format: "%0.2d", s))
value = value.replacingOccurrences(of: "dd", with: String(format: "%d", d))
if (ago) {
value += " ago"
}
return value
}

}

converted into an swift 2 extension + variable format :

extension NSTimeInterval {

func timeIntervalAsString(format format : String = "hh:mm:ss:sss") -> String {
let ms = Int((self % 1) * 1000)
let asInt = NSInteger(self)
let s = asInt % 60
let m = (asInt / 60) % 60
let h = (asInt / 3600)

var value = format
value = value.replace("hh", replacement: String(format: "%0.2d", h))
value = value.replace("mm", replacement: String(format: "%0.2d", m))
value = value.replace("sss", replacement: String(format: "%0.3d", ms))
value = value.replace("ss", replacement: String(format: "%0.2d", s))
return value
}

}

extension String {
/**
Replaces all occurances from string with replacement
*/
public func replace(string:String, replacement:String) -> String {
return self.stringByReplacingOccurrencesOfString(string, withString: replacement, options: NSStringCompareOptions.LiteralSearch, range: nil)
}

}

for convert hour and minutes to seconds in swift 2.0:

///RETORNA TOTAL DE SEGUNDOS DE HORA:MINUTOS
func horasMinutosToSeconds (HoraMinutos:String) -> Int {

let formatar = NSDateFormatter()
let calendar = NSCalendar.currentCalendar()
formatar.locale = NSLocale.currentLocale()
formatar.dateFormat = "HH:mm"

let Inicio = formatar.dateFromString(HoraMinutos)
let comp = calendar.components([NSCalendarUnit.Hour, NSCalendarUnit.Minute], fromDate: Inicio!)

let hora = comp.hour
let minute = comp.minute

let hours = hora*3600
let minuts = minute*60

let totseconds = hours+minuts

return totseconds
}

Equivalent in Objective-C, based on the @matthias-bauch answer.

+ (NSString *)stringFromTimeInterval:(NSTimeInterval)timeInterval
{
NSInteger interval = timeInterval;
NSInteger ms = (fmod(timeInterval, 1) * 1000);
long seconds = interval % 60;
long minutes = (interval / 60) % 60;
long hours = (interval / 3600);

return [NSString stringWithFormat:@"%0.2ld:%0.2ld:%0.2ld,%0.3ld", hours, minutes, seconds, (long)ms];
}