Swift&Cocoa实战之数据类型:时间日期

概述时间日期 NSDate 在Objective-C中，可以使用如下的代码创建一个UTC的时间： NSDate *currentUTCDate = [NSDate date] 但是在Swift中，如果使用如下方式： let date = NSDate() 获取到的会是本地时间。 UTC时间与本地化时间 import UIKitlet date = NSDate();// "Apr 1, 2015 时间日期 NSDate

在Objective-C中，可以使用如下的代码创建一个UTC的时间：

NSDate *currentUTcdate = [NSDate date]

但是在Swift中，如果使用如下方式：

let date = NSDate()

获取到的会是本地时间。

UTC时间与本地化时间

import UIKitlet date = NSDate();// "Apr 1,2015,8:53 AM" <-- local without secondsvar formatter = NSDateFormatter();formatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZ";let defaultTimeZonestr = formatter.stringFromDate(date);// "2015-04-01 08:52:00 -0400" <-- same date,local,but with secondsformatter.timeZone = NSTimeZone(abbreviation: "UTC");let utcTimeZonestr = formatter.stringFromDate(date);// "2015-04-01 12:52:00 +0000" <-- same date,Now in UTC

时间比较

如果需要比较两个日期，可以使用如下方法，在如下代码中已经展示了如何处理不同的返回结果：

// Date comparision to compare current date and end date.var dateComparisionResult:NSComparisonResult = NSDate().compare(endDate)if dateComparisionResult == NSComparisonResult.OrderedAscending{    // Current date is smaller than end date.}else if dateComparisionResult == NSComparisonResult.OrderedDescending{    // Current date is greater than end date.}else if dateComparisionResult == NSComparisonResult.OrderedSame{    // Current date and end date are same.}

TimeStamp

如果需要将某个TimeStamp("/Date(1427909016000-0800)”)转化为NSDate对象，那么可以使用如下的扩展工具，该扩展将会把TimeStamp转化为本地化时间。其中1427909016000表示从Unix计时以来的毫秒数，而-0800表示时区：

extension NSDate {    convenIEnce init?(JsonDate: String) {        let prefix = "/Date("        let suffix = ")/"        let scanner = NSScanner(string: JsonDate)                // Check prefix:        if scanner.scanString(prefix,intoString: nil) {                        // Read milliseconds part:            var milliseconds : Int64 = 0            if scanner.scanLongLong(&milliseconds) {                // Milliseconds to seconds:                var timeStamp = NSTimeInterval(milliseconds)/1000.0                                // Read optional timezone part:                var timeZoneOffset : Int = 0                if scanner.scanInteger(&timeZoneOffset) {                    let hours = timeZoneOffset / 100                    let minutes = timeZoneOffset % 100                    // Adjust timestamp according to timezone:                    timeStamp += NSTimeInterval(3600 * hours + 60 * minutes)                }                                // Check suffix:                if scanner.scanString(suffix,intoString: nil) {                    // Success! Create NSDate and return.                    self.init(timeIntervalSince1970: timeStamp)                    return                }            }        }                // Wrong format,return nil. (The compiler requires us to        // do an initialization first.)        self.init(timeIntervalSince1970: 0)        return nil    }}

使用的例子如下：

if let theDate = NSDate(JsonDate: "/Date(1427909016000-0800)/"){    println(theDate)}else{    println("wrong format")}

NSDateFormatter：格式化时间

var dataString = "April 1,2015" as Stringvar dateFormatter = NSDateFormatter()dateFormatter.dateFormat = "MM-dd-yyyy"dateFormatter.timeZone = NSTimeZone.localTimeZone()// convert string into datelet dateValue = dateFormatter.dateFromString(dataString) as NSDate!println(dateValue)

NSCalendar

// Playground - noun: a place where people can playimport UIKit// Setup the calendar objectlet calendar = NSCalendar.currentCalendar()// Set up date objectlet date = NSDate()// Create an NSDate for the first and last day of the month//let components = calendar.components(NSCalendarUnit.CalendarUnitYear |//                                     NSCalendarUnit.CalendarUnitMonth |//                                     NSCalendarUnit.WeekdayCalendarUnit |//                                     NSCalendarUnit.WeekCalendarUnit |//                                     NSCalendarUnit.CalendarUnitDay,//                                     fromDate: date)// Create an NSDate for the first and last day of the monthlet components = NSCalendar.currentCalendar().components(NSCalendarUnit.CalendarUnitMonth,fromDate: date)components.month// Getting the First and Last date of the monthcomponents.day = 1let firstDateOfMonth: NSDate = calendar.dateFromComponents(components)!components.month  += 1components.day     = 0let lastDateOfMonth: NSDate = calendar.dateFromComponents(components)!var unitFlags = NSCalendarUnit.WeekOfMonthCalendarUnit |                NSCalendarUnit.WeekdayCalendarUnit     |                NSCalendarUnit.CalendarUnitDaylet firstDateComponents = calendar.components(unitFlags,fromDate: firstDateOfMonth)let lastDateComponents  = calendar.components(unitFlags,fromDate: lastDateOfMonth)// Sun = 1,Sat = 7let firstWeek = firstDateComponents.weekOfMonthlet lastWeek  = lastDateComponents.weekOfMonthlet numOfDatestoprepend = firstDateComponents.weekday - 1let numOfDatesToAppend  = 7 - lastDateComponents.weekday + (6 - lastDateComponents.weekOfMonth) * 7let startDate: NSDate = calendar.dateByAddingUnit(NSCalendarUnit.CalendarUnitDay,value: -numOfDatestoprepend,toDate: firstDateOfMonth,options: nil)!let endDate:   NSDate = calendar.dateByAddingUnit(NSCalendarUnit.CalendarUnitDay,value: numOfDatesToAppend,toDate: lastDateOfMonth,options: nil)!Array(map(0..<42) {    calendar.dateByAddingUnit(NSCalendarUnit.CalendarUnitDay,value: ,toDate: startDate,options: nil)!})"\(components.year)"var dateString = "2014-10-3" // change to your date formatvar dateFormatter = NSDateFormatter()dateFormatter.dateFormat = "YYYY-MM-dd"var someDate = dateFormatter.dateFromString(dateString)println(someDate)

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