Swiftで現在からの経過時間を計算するNSDateのExtension

Swiftでつかえる、TwitterやFacebookのような現在からの経過時間を計算するライブラリをExtensionで作りました。「1sec,2minutes,3hours,4days」と表示するアレです。

ソース

TimeInterval+NSDate.swift

import UIKit

extension NSDate {
    func stringForTimeIntervalSinceCreated() -> String {
        return stringForTimeIntervalSinceCreated(nowDate:NSDate())

    }

    func stringForTimeIntervalSinceCreated(#nowDate:NSDate) -> String {
        var MinInterval  :Int = 0
        var HourInterval :Int = 0
        var DayInterval  :Int = 0
        var DayModules   :Int = 0
        let interval = abs(Int(self.timeIntervalSinceDate(nowDate)))
        if (interval >= 86400) {
            DayInterval = interval/86400
            DayModules = interval%86400
            if (DayModules != 0) {
                if (DayModules>=3600) {
                    //HourInterval=DayModules/3600;
                    return String(DayInterval) + " days"
                } else {
                    if (DayModules >= 60) {
                        //MinInterval=DayModules/60;
                        return String(DayInterval) + " days"
                    } else {
                        return String(DayInterval) + " days"
                    }
                }
            } else {
                return String(DayInterval) + " days"
            }
        } else {
            if (interval >= 3600) {
                HourInterval = interval/3600
                return String(HourInterval) + " hours"
            } else if (interval >= 60) {
                MinInterval = interval/60
                return String(MinInterval) + " minutes"
            } else {
                return String(interval) + " sec"
            }
        }
    }
}

extension NSDate {
    func toString(#format:String, localeIdentifier:String = "ja_JP") -> String? {
        let formatter = NSDateFormatter()
        formatter.dateFormat = format
        formatter.locale = NSLocale(localeIdentifier: localeIdentifier)
        let dateStr = formatter.stringFromDate(self)
        return dateStr
    }
}

extension String {
    func toDate(#format:String, localeIdentifier:String = "ja_JP") -> NSDate? {
        let formatter = NSDateFormatter()
        formatter.dateFormat = format
        formatter.locale = NSLocale(localeIdentifier: localeIdentifier)
        let date = formatter.dateFromString(self)
        return date
    }
}

使い方

その１

TimeInterval+NSDate.swift

if let createdDate = "2015-02-01 14:54:09".toDate(format: "yyyy-M-d HH:mm:ss") {
    let a = createdDate.stringForTimeIntervalSinceCreated() // non optional
    println(a) // "5 days"
}

その２

TimeInterval+NSDate.swift

var createdDate = "2015-02-06 14:54:09".toDate(format: "yyyy-M-d HH:mm:ss")
var b = createdDate?.stringForTimeIntervalSinceCreated() // optional
println(b) // Optional("4 hours")

その３

TimeInterval+NSDate.swift

var c = "2015-02-06 19:48:31".toDate(format: "yyyy-M-d HH:mm:ss")?.stringForTimeIntervalSinceCreated() // optional
println(c) // Optional("5 days")

引用 http://hayatomo.com/2015/02/09/1504