How to parse an ISO-8601 duration in Objective C?

Question

I'm looking for an easy way to parse a string that contains an ISO-8601 duration in Objective C. The result should be something usable like a NSTimeInterval.

An example of an ISO-8601 duration: P1DT13H24M17S, which means 1 day, 13 hours, 24 minutes and 17 seconds.

Answer 1

If you know exactly which fields you'll be getting, you can use one invocation of sscanf():

const char *stringToParse = ...;
int days, hours, minutes, seconds;
NSTimeInterval interval;
if(sscanf(stringToParse, "P%dDT%dH%dM%sS", &days, &hours, &minutes, &seconds) == 4)
    interval = ((days * 24 + hours) * 60 + minutes) * 60 + seconds;
else
    ; // handle error, parsing failed

If any of the fields might be omitted, you'll need to be a little smarter in your parsing, e.g.:

const char *stringToParse = ...;
int days = 0, hours = 0, minutes = 0, seconds = 0;

const char *ptr = stringToParse;
while(*ptr)
{
    if(*ptr == 'P' || *ptr == 'T')
    {
        ptr++;
        continue;
    }

    int value, charsRead;
    char type;
    if(sscanf(ptr, "%d%c%n", &value, &type, &charsRead) != 2)
        ;  // handle parse error
    if(type == 'D')
        days = value;
    else if(type == 'H')
        hours = value;
    else if(type == 'M')
        minutes = value;
    else if(type == 'S')
        seconds = value;
    else
        ;  // handle invalid type

    ptr += charsRead;
}

NSTimeInterval interval = ((days * 24 + hours) * 60 + minutes) * 60 + seconds;

Answer 2

A pure Objective C version...

NSString *duration = @"P1DT10H15M49S";

int i = 0, days = 0, hours = 0, minutes = 0, seconds = 0;

while(i < duration.length)
{
    NSString *str = [duration substringWithRange:NSMakeRange(i, duration.length-i)];

    i++;

    if([str hasPrefix:@"P"] || [str hasPrefix:@"T"])
        continue;

    NSScanner *sc = [NSScanner scannerWithString:str];
    int value = 0;

    if ([sc scanInt:&value])
    {
        i += [sc scanLocation]-1;

        str = [duration substringWithRange:NSMakeRange(i, duration.length-i)];

        i++;

        if([str hasPrefix:@"D"])
            days = value;
        else if([str hasPrefix:@"H"])
            hours = value;
        else if([str hasPrefix:@"M"])
            minutes = value;
        else if([str hasPrefix:@"S"])
            seconds = value;
    }
}

NSLog(@"%@", [NSString stringWithFormat:@"%d days, %d hours, %d mins, %d seconds", days, hours, minutes, seconds]);

Answer 3

This version parse every youtube duration without errors.
Important: This version use ARC.

- (NSString*)parseISO8601Time:(NSString*)duration
{
    NSInteger hours = 0;
    NSInteger minutes = 0;
    NSInteger seconds = 0;

    //Get Time part from ISO 8601 formatted duration http://en.wikipedia.org/wiki/ISO_8601#Durations
    duration = [duration substringFromIndex:[duration rangeOfString:@"T"].location];

    while ([duration length] > 1) { //only one letter remains after parsing
        duration = [duration substringFromIndex:1];

        NSScanner *scanner = [[NSScanner alloc] initWithString:duration];

        NSString *durationPart = [[NSString alloc] init];
        [scanner scanCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] intoString:&durationPart];

        NSRange rangeOfDurationPart = [duration rangeOfString:durationPart];

        duration = [duration substringFromIndex:rangeOfDurationPart.location + rangeOfDurationPart.length];

        if ([[duration substringToIndex:1] isEqualToString:@"H"]) {
            hours = [durationPart intValue];
        }
        if ([[duration substringToIndex:1] isEqualToString:@"M"]) {
            minutes = [durationPart intValue];
        }
        if ([[duration substringToIndex:1] isEqualToString:@"S"]) {
            seconds = [durationPart intValue];
        }
    }

    return [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];
}

Answer 4

Swift2 implementation: https://github.com/Igor-Palaguta/YoutubeEngine/blob/swift-2.3/YoutubeEngine/Classes/Parser/NSDateComponents+ISO8601.swift

Example: let components = NSDateComponents(ISO8601String: "P1Y2M3DT4H5M6S")

Tests: https://github.com/Igor-Palaguta/YoutubeEngine/blob/swift-2.3/Example/Tests/ISO8601DurationTests.swift

It also correctly handles "P1M" and "PT1M" cases

Swift3 implementation: https://github.com/Igor-Palaguta/YoutubeEngine/blob/master/Source/YoutubeEngine/Parser/NSDateComponents%2BISO8601.swift

Example: let components = dateComponents(ISO8601String: "P1Y2M3DT4H5M6S")

Tests: https://github.com/Igor-Palaguta/YoutubeEngine/blob/master/Tests/YoutubeEngineTests/ISO8601DurationTests.swift

Update 20.01.2017: Added support for weeks

Answer 5

slightly modifying function of the user

Sergei Pekar

+ (NSString*)parseISO8601Time:(NSString*)duration
{
    NSInteger hours = 0;
    NSInteger minutes = 0;
    NSInteger seconds = 0;

    //Get Time part from ISO 8601 formatted duration http://en.wikipedia.org/wiki/ISO_8601#Durations
    if ([duration rangeOfString:@"T"].location == NSNotFound || [duration rangeOfString:@"P"].location == NSNotFound) {
        NSLog(@"Time is not a part from ISO 8601 formatted duration");
        return @"0:00 Error";
    }

    duration = [duration substringFromIndex:[duration rangeOfString:@"T"].location];

    while ([duration length] > 1) { //only one letter remains after parsing
        duration = [duration substringFromIndex:1];

        NSScanner *scanner = [[NSScanner alloc] initWithString:duration];
        NSString *durationPart = [[NSString alloc] init];
        [scanner scanCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] intoString:&durationPart];

        NSRange rangeOfDurationPart = [duration rangeOfString:durationPart];

        if ((rangeOfDurationPart.location + rangeOfDurationPart.length) > duration.length) {
            NSLog(@"Time is not a part from ISO 8601 formatted duration");
            return @"0:00 Error";
        }

        duration = [duration substringFromIndex:rangeOfDurationPart.location + rangeOfDurationPart.length];

        if ([[duration substringToIndex:1] isEqualToString:@"H"]) {
            hours = [durationPart intValue];
        }
        if ([[duration substringToIndex:1] isEqualToString:@"M"]) {
            minutes = [durationPart intValue];
        }
        if ([[duration substringToIndex:1] isEqualToString:@"S"]) {
            seconds = [durationPart intValue];
        }
    }

    if (hours != 0)
        return [NSString stringWithFormat:@"%ld:%02ld:%02ld", (long)hours, (long)minutes, (long)seconds];
    else
        return [NSString stringWithFormat:@"%ld:%02ld", (long)minutes, (long)seconds];
}

Answer 6

Here is an example for swift: (only for hours, minutes and seconds)

func parseDuration(duration: String) -> Int {

var days = 0
var hours = 0
var minutes = 0
var seconds = 0

var decisionMaker = 0
var factor = 1

let specifiers: [Character] = ["M", "H", "T", "P"]

let length = count(duration)

for i in 1...length {

    let index = advance(duration.startIndex, length - i)
    let char = duration[index]

    for specifier in specifiers {
        if char == specifier {
            decisionMaker++
            factor = 1
        }
    }

    if let value = String(char).toInt() {

        switch decisionMaker {
            case 0:
                seconds += value * factor
                factor *= 10
            case 1:
                minutes += value * factor
                factor *= 10
            case 2:
                hours += value * factor
                factor *= 10
            case 4:
                days += value * factor
                factor *= 10
            default:
                break
        }
    }

}

return seconds + (minutes * 60) + (hours * 3600) + (days * 3600 * 24)
}

Answer 7

Here is swift 3 version of headkaze example: This format was most suitable in my case:

private func parseISO8601Time(iso8601: String) -> String {

    let nsISO8601 = NSString(string: iso8601)

    var days = 0, hours = 0, minutes = 0, seconds = 0
    var i = 0

    while i < nsISO8601.length  {

        var str = nsISO8601.substring(with: NSRange(location: i, length: nsISO8601.length - i))

        i += 1

        if str.hasPrefix("P") || str.hasPrefix("T") { continue }

        let scanner = Scanner(string: str)
        var value = 0

        if scanner.scanInt(&value) {

            i += scanner.scanLocation - 1

            str = nsISO8601.substring(with: NSRange(location: i, length: nsISO8601.length - i))

            i += 1

            if str.hasPrefix("D") {
                days = value
            } else if str.hasPrefix("H") {
                hours = value
            } else if str.hasPrefix("M") {
                minutes = value
            } else if str.hasPrefix("S") {
                seconds = value
            }
        }
    }

    if days > 0 {
        hours += 24 * days
    }

    if hours > 0 {
        return String(format: "%d:%02d:%02d", hours, minutes, seconds)
    }

    return String(format: "%d:%02d", minutes, seconds)

}

Answer 8

I looked up this Wikipedia article for a reference to how ISO-8601 actually works. I'm no Cocoa expert, but I'm betting if you can parse that string and extract the component hour, minute, second, day, etc., getting it in to an NSTimeInterval should be easy. The tricky part is parsing it. I'd probably do it something like this:

First, split the string in to two separate strings: one representing the days, and one representing the times. NSString has an instance method componentsSeparatedByString:NSString that returns an NSArray of substrings of your original NSString separated by the parameter you pass in. It would look something like this:

NSString* iso8601 = /*However you're getting your string in*/
NSArray* iso8601Parts = [iso8601 componentsSeparatedByString:@"T"];

Next, search the first element of iso8601Parts for each of the possible day duration indicators (Y, M, W, and D). When you find one, grab all the preceeding digits (and possibly a decimal point), cast them to a float, and store them somewhere. Remember that if there was only a time element, then iso8601Parts[0] will be the empty string.

Then, do the same thing looking for time parts in the second element of iso8601Parts for possible time indicators (H, M, S). Remember that if there was only a day component (that is, there was no 'T' character in the original string), then iso8601Parts will only be of length one, and an attempt to access the second element will cause an out of bounds exception.

An NSTimeInterval is just a long storing a number of seconds, so convert the individual pieces you pulled out in to seconds, add them together, store them in your NSTimeInterval, and you're set.

Sorry, I know you asked for an "easy" way to do it, but based on my (admittedly light) searching around and knowledge of the API, this is the easiest way to do it.

Answer 9

Quick and dirty implementation

    - (NSInteger)integerFromYoutubeDurationString:(NSString*)duration{

    if(duration == nil){
        return 0;
    }

    NSString *startConst = @"PT";
    NSString *hoursConst = @"H";
    NSString *minutesConst = @"M";
    NSString *secondsConst = @"S";
    NSString *hours = nil;
    NSString *minutes = nil;
    NSString *seconds = nil;
    NSInteger totalSeconds = 0;

    NSString *clean = [duration componentsSeparatedByString:startConst][1];

    if([clean containsString:hoursConst]){
        hours = [clean componentsSeparatedByString:hoursConst][0];
        clean = [clean componentsSeparatedByString:hoursConst][1];
        totalSeconds = [hours integerValue]*3600;
    }
    if([clean containsString:minutesConst]){
        minutes = [clean componentsSeparatedByString:minutesConst][0];
        clean = [clean componentsSeparatedByString:minutesConst][1];
        totalSeconds = totalSeconds + [minutes integerValue]*60;
    }
    if([clean containsString:secondsConst]){
        seconds = [clean componentsSeparatedByString:secondsConst][0];
        totalSeconds = totalSeconds + [seconds integerValue];
    }

    return totalSeconds;
}

Answer 10

There are answers already, but I ended up implementing yet another version using NSScanner. This version ignores year and month since they cannot be converted to number of seconds.

static NSTimeInterval timeIntervalFromISO8601Duration(NSString *duration) {
    NSTimeInterval timeInterval = 0;
    NSScanner *scanner = [NSScanner scannerWithString:duration];

    NSCharacterSet *designators = [NSCharacterSet characterSetWithCharactersInString:@"PYMWDTHMS"];
    BOOL isScanningTime = NO;

    while (![scanner isAtEnd]) {
        double scannedNumber = 0;
        BOOL didScanNumber = [scanner scanDouble:&scannedNumber];

        NSString *scanned = nil;
        if ([scanner scanCharactersFromSet:designators intoString:&scanned]) {
            if (didScanNumber) {
                switch ([scanned characterAtIndex:0]) {
                    case 'D':
                        timeInterval += scannedNumber * 60 * 60 * 24;
                        break;
                    case 'H':
                        timeInterval += scannedNumber * 60 * 60;
                        break;
                    case 'M':
                        if (isScanningTime) {
                            timeInterval += scannedNumber * 60;
                        }
                        break;
                    case 'S':
                        timeInterval += scannedNumber;
                        break;
                    default:
                        break;
                }
            }

            if ([scanned containsString:@"T"]) {
                isScanningTime = YES;
            }
        }
    }

    return timeInterval;
}

Answer 11

Now in Swift! (Yes it's a little long, but it handles all cases and singular/plural).

Handles Years, Months, Weeks, Days, Hours, Minutes, and Seconds!

func convertFromISO8601Duration(isoValue: AnyObject) -> String? {

    var displayedString: String?
    var hasHitTimeSection = false
    var isSingular = false

    if let isoString = isoValue as? String {

        displayedString = String()

        for val in isoString {


            if val == "P" {
                // Do nothing when parsing the 'P'
                continue

            }else if val == "T" {
                // Indicate that we are now dealing with the 'time section' of the ISO8601 duration, then carry on.
                hasHitTimeSection = true
                continue
            }

            var tempString = String()

            if val >= "0" && val <= "9" {

                // We need to know whether or not the value is singular ('1') or not ('11', '23').
                if let safeDisplayedString = displayedString as String!
                    where count(displayedString!) > 0 && val == "1" {

                    let lastIndex = count(safeDisplayedString) - 1

                    let lastChar = safeDisplayedString[advance(safeDisplayedString.startIndex, lastIndex)]

                        //test if the current last char in the displayed string is a space (" "). If it is then we will say it's singular until proven otherwise.
                    if lastChar == " " {
                        isSingular = true
                    } else {
                        isSingular = false
                    }
                }
                else if val == "1" {
                    // if we are just dealing with a '1' then we will say it's singular until proven otherwise.
                    isSingular = true
                }
                else {
                    // ...otherwise it's a plural duration.
                    isSingular = false
                }

                tempString += "\(val)"

                displayedString! += tempString

            } else {

                // handle the duration type text. Make sure to use Months & Minutes correctly.
                switch val {

                case "Y", "y":

                    if isSingular {
                        tempString += " Year "
                    } else {
                        tempString += " Years "
                    }

                    break

                case "M", "m":

                    if hasHitTimeSection {

                        if isSingular {
                            tempString += " Minute "
                        } else {
                            tempString += " Minutes "
                        }
                    }
                    else {

                        if isSingular {
                            tempString += " Month "
                        } else {
                            tempString += " Months "
                        }
                    }

                    break

                case "W", "w":

                    if isSingular {
                        tempString += " Week "
                    } else {
                        tempString += " Weeks "
                    }

                    break

                case "D", "d":

                    if isSingular {
                        tempString += " Day "
                    } else {
                        tempString += " Days "
                    }

                    break

                case "H", "h":

                    if isSingular {
                        tempString += " Hour "
                    } else {
                        tempString += " Hours "
                    }

                    break

                case "S", "s":

                    if isSingular {
                        tempString += " Second "
                    } else {
                        tempString += " Seconds "
                    }

                    break

                default:
                    break

                }

                // reset our singular flag, since we're starting a new duration.
                isSingular = false

                displayedString! += tempString

            }

        }

    }

    return displayedString
}

Answer 12

Swift 4.2 version

Works with years, months, days, hours, minutes, seconds. Seconds can be float number.

extension String{
    public func parseISO8601Time() -> Duration {

        let nsISO8601 = NSString(string: self)

        var days = 0, hours = 0, minutes = 0, seconds: Float = 0, weeks = 0, months = 0, years = 0
        var i = 0

        var beforeT:Bool = true

        while i < nsISO8601.length  {

            var str = nsISO8601.substring(with: NSRange(location: i, length: nsISO8601.length - i))

            i += 1

            if str.hasPrefix("P") || str.hasPrefix("T") {
                beforeT = !str.hasPrefix("T")
                continue
            }

            let scanner = Scanner(string: str)
            var value: Float = 0

            if scanner.scanFloat(&value) {

                i += scanner.scanLocation - 1

                str = nsISO8601.substring(with: NSRange(location: i, length: nsISO8601.length - i))

                i += 1

                if str.hasPrefix("Y") {
                    years = Int(value)
                } else if str.hasPrefix("M") {
                    if beforeT{
                        months = Int(value)
                    }else{
                        minutes = Int(value)
                    }
                } else if str.hasPrefix("W") {
                    weeks = Int(value)
                } else if str.hasPrefix("D") {
                    days = Int(value)
                } else if str.hasPrefix("H") {
                    hours = Int(value)
                } else if str.hasPrefix("S") {
                    seconds = value
                }
            }
        }

        return Duration(years: years, months: months, weeks: weeks, days: days, hours: hours, minutes: minutes, seconds: seconds)
}      

Duration struct:

public struct Duration {

let daysInMonth: Int = 30
let daysInYear: Int = 365

var years: Int
var months: Int
var weeks: Int
var days: Int
var hours: Int
var minutes: Int
var seconds: Float

public func getMilliseconds() -> Int{
    return Int(round(seconds*1000)) + minutes*60*1000 + hours*60*60*1000 + days*24*60*60*1000 + weeks*7*24*60*60*1000 + months*daysInMonth*24*60*60*1000 + years*daysInYear*24*60*60*1000
}

public func getFormattedString() -> String{

    var formattedString = ""

    if years != 0{
        formattedString.append("\(years)")
        formattedString.append(" ")
        formattedString.append(years == 1 ? "year".localized() : "years".localized())
        formattedString.append(" ")
    }

    if months != 0{
        formattedString.append("\(months)")
        formattedString.append(" ")
        formattedString.append(months == 1 ? "month".localized() : "months".localized())
        formattedString.append(" ")
    }

    if weeks != 0{
        formattedString.append("\(weeks)")
        formattedString.append(" ")
        formattedString.append(weeks == 1 ? "week".localized() : "weeks".localized())
        formattedString.append(" ")
    }

    if days != 0{
        formattedString.append("\(days)")
        formattedString.append(" ")
        formattedString.append(days == 1 ? "day".localized() : "days".localized())
        formattedString.append(" ")
    }

    if seconds != 0{
        formattedString.append(String(format: "%02d:%02d:%.02f", hours, minutes, seconds))
    }else{
        formattedString.append(String(format: "%02d:%02d", hours, minutes))
    }

    return formattedString
}

}