Swifty Date Formats

DateFormat.swift

struct DateFormat: DateFormatConvertible {
    let dateFormat: String

    init() {
        dateFormat = ""
    }

    init(format: DateFormatConvertible) {
        dateFormat = format.dateFormat
    }

    init(formats: [DateFormatConvertible]) {
        dateFormat = formats.reduce("", +).dateFormat
    }

    func year(_ style: YearStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func quarter(_ style: QuarterStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func month(_ style: MonthStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func day(_ style: DayStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func hour(_ style: HourStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func minute(_ style: MinuteStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func second(_ style: SecondStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func timezone(_ style: TimeZoneStyle) -> DateFormat {
        return DateFormat(formats: [dateFormat, style])
    }

    func separator(_ separator: Separator) -> DateFormat {
        return DateFormat(formats: [dateFormat, separator])
    }

    func string(_ string: String) -> DateFormat {
        return DateFormat(formats: [dateFormat, "'", string, "'"])
    }
}

extension DateFormatter {
    func setDateFormat(_ format: DateFormatConvertible) {
        dateFormat = format.dateFormat
    }
}

DateFormatConvertible.swift

protocol DateFormatConvertible {
    var dateFormat: String { get }
}

extension String: DateFormatConvertible {
    var dateFormat: String { return self }
}

func + (lhs: DateFormatConvertible, rhs: DateFormatConvertible) -> DateFormatConvertible {
    return lhs.dateFormat + rhs.dateFormat
}

Example.swift

//yyyy-MM-dd'T'HH:mm:ssZ

let format = DateFormat()
    .year(.fourDigits)
    .separator(.dash)
    .month(.zeroPaddedNumber)
    .separator(.dash)
    .day(.zeroPaddedNumber)
    .string("T")
    .hour(.zeroPaddedTwentyFourHour)
    .separator(.colon)
    .minute(.zeroPaddedNumber)
    .separator(.colon)
    .second(.zeroPaddedNumber)
    .timezone(.RFC822)

let formatter = DateFormatter()
formatter.setDateFormat(format)

print(format.dateFormat) //yyyy-MM-dd'T'HH:mm:ssZ

Styles.swift

//TODO Adopt TR-35 (http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Format_Patterns)

//MARK :- Styles

enum YearStyle: String, DateFormatConvertible {
    case noPadding = "y"
    case twoDigits = "yy"
    case fourDigits = "yyyy"

    var dateFormat: String { return rawValue }
}

enum QuarterStyle: String, DateFormatConvertible {
    case number = "Q"
    case zeroPaddedNumber = "QQ"
    case qAndNumber = "QQQ"
    case spelledOut = "QQQQ"

    var dateFormat: String { return rawValue }
}

enum MonthStyle: String, DateFormatConvertible {
    case number = "M"
    case zeroPaddedNumber = "MM"
    case shortName = "MMM"
    case fullName = "MMMM"
    case narrowName = "MMMMM"

    var dateFormat: String { return rawValue }
}

enum DayStyle: String, DateFormatConvertible {
    case number = "d"
    case zeroPaddedNumber = "dd"
    case dayOfWeekInMonth = "F"
    case shortDayOfWeek = "E"
    case fullDayOfWeek = "EEEE"
    case narrowDayOfWeek = "EEEEE"

    var dateFormat: String { return rawValue }
}

enum HourStyle: String, DateFormatConvertible {
    case twelveHour = "h"
    case zeroPaddedTwelveHour = "hh"
    case twentyFourHour = "H"
    case zeroPaddedTwentyFourHour = "HH"
    case AMorPM = "a"

    var dateFormat: String { return rawValue }
}

enum MinuteStyle: String, DateFormatConvertible {
    case number = "m"
    case zeroPaddedNumber = "mm"

    var dateFormat: String { return rawValue }
}

enum SecondStyle: String, DateFormatConvertible {
    case number = "s"
    case zeroPaddedNumber = "ss"

    var dateFormat: String { return rawValue }
}

enum TimeZoneStyle: String, DateFormatConvertible {
    case threeLetterName = "zzz"
    case expandedName = "zzzz"
    case RFC822 = "Z"
    case ISO8601 = "ZZZZZ"

    var dateFormat: String { return rawValue }
}

enum Separator: String, DateFormatConvertible {
    case dash = "-"
    case slash = "/"
    case colon = ":"
    case space = " "

    var dateFormat: String { return rawValue }
}