问获取Swift中两个日期(月/日/小时/分钟/秒)之间的差值

EN

let exampleDate = Date().addingTimeInterval(-15000)

let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .full
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())

print(relativeDate) // 4 hours ago

   func dateDiff(dateStr:String) -> String {
            var f:NSDateFormatter = NSDateFormatter()
            f.timeZone = NSTimeZone.localTimeZone()
            f.dateFormat = "yyyy-M-dd'T'HH:mm:ss.SSSZZZ"

            var now = f.stringFromDate(NSDate())
            var startDate = f.dateFromString(dateStr)
            var endDate = f.dateFromString(now)
            var calendar: NSCalendar = NSCalendar.currentCalendar()

            let calendarUnits = NSCalendarUnit.CalendarUnitWeekOfMonth | NSCalendarUnit.CalendarUnitDay | NSCalendarUnit.CalendarUnitHour | NSCalendarUnit.CalendarUnitMinute | NSCalendarUnit.CalendarUnitSecond
            let dateComponents = calendar.components(calendarUnits, fromDate: startDate!, toDate: endDate!, options: nil)

            let weeks = abs(dateComponents.weekOfMonth)
            let days = abs(dateComponents.day)
            let hours = abs(dateComponents.hour)
            let min = abs(dateComponents.minute)
            let sec = abs(dateComponents.second)

            var timeAgo = ""

            if (sec > 0){
                if (sec > 1) {
                    timeAgo = "\(sec) Seconds Ago"
                } else {
                    timeAgo = "\(sec) Second Ago"
                }
            }

            if (min > 0){
                if (min > 1) {
                    timeAgo = "\(min) Minutes Ago"
                } else {
                    timeAgo = "\(min) Minute Ago"
                }
            }

            if(hours > 0){
                if (hours > 1) {
                    timeAgo = "\(hours) Hours Ago"
                } else {
                    timeAgo = "\(hours) Hour Ago"
                }
            }

            if (days > 0) {
                if (days > 1) {
                    timeAgo = "\(days) Days Ago"
                } else {
                    timeAgo = "\(days) Day Ago"
                }
            }

            if(weeks > 0){
                if (weeks > 1) {
                    timeAgo = "\(weeks) Weeks Ago"
                } else {
                    timeAgo = "\(weeks) Week Ago"
                }
            }

            print("timeAgo is===> \(timeAgo)")
            return timeAgo;
        }

extension Date {
    /// Returns the amount of years from another date
    func years(from date: Date) -> Int {
        return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
    }
    /// Returns the amount of months from another date
    func months(from date: Date) -> Int {
        return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
    }
    /// Returns the amount of weeks from another date
    func weeks(from date: Date) -> Int {
        return Calendar.current.dateComponents([.weekOfYear], from: date, to: self).weekOfYear ?? 0
    }
    /// Returns the amount of days from another date
    func days(from date: Date) -> Int {
        return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
    }
    /// Returns the amount of hours from another date
    func hours(from date: Date) -> Int {
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }
    /// Returns the amount of minutes from another date
    func minutes(from date: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }
    /// Returns the amount of seconds from another date
    func seconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
    }
    /// Returns the a custom time interval description from another date
    func offset(from date: Date) -> String {
        if years(from: date)   > 0 { return "\(years(from: date))y"   }
        if months(from: date)  > 0 { return "\(months(from: date))M"  }
        if weeks(from: date)   > 0 { return "\(weeks(from: date))w"   }
        if days(from: date)    > 0 { return "\(days(from: date))d"    }
        if hours(from: date)   > 0 { return "\(hours(from: date))h"   }
        if minutes(from: date) > 0 { return "\(minutes(from: date))m" }
        if seconds(from: date) > 0 { return "\(seconds(from: date))s" }
        return ""
    }

    func offsetLong(from date: Date) -> String {
        if years(from: date)   > 0 { return years(from: date) > 1 ? "\(years(from: date)) years ago" : "\(years(from: date)) year ago" }
        if months(from: date)  > 0 { return months(from: date) > 1 ? "\(months(from: date)) months ago" : "\(months(from: date)) month ago" }
        if weeks(from: date)   > 0 { return weeks(from: date) > 1 ? "\(weeks(from: date)) weeks ago" : "\(weeks(from: date)) week ago"   }
        if days(from: date)    > 0 { return days(from: date) > 1 ? "\(days(from: date)) days ago" : "\(days(from: date)) day ago" }
        if hours(from: date)   > 0 { return hours(from: date) > 1 ? "\(hours(from: date)) hours ago" : "\(hours(from: date)) hour ago"   }
        if minutes(from: date) > 0 { return minutes(from: date) > 1 ? "\(minutes(from: date)) minutes ago" : "\(minutes(from: date)) minute ago" }
        if seconds(from: date) > 0 { return seconds(from: date) > 1 ? "\(seconds(from: date)) seconds ago" : "\(seconds(from: date)) second ago" }
        return ""
    }

}