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Swift&Cocoa实战之数据类型中的时间日期

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 UIKit  let date = NSDate(); // "Apr 1, 2015, 8:53 AM" <-- local without seconds  var 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 seconds formatter.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 String var dateFormatter = NSDateFormatter() dateFormatter.dateFormat = "MM-dd-yyyy" dateFormatter.timeZone = NSTimeZone.localTimeZone()  // convert string into date let dateValue = dateFormatter.dateFromString(dataString) as NSDate!  println(dateValue)

Swift&Cocoa实战之数据类型中的时间日期

NSCalendar

// Playground - noun: a place where people can play import UIKit // Setup the calendar object let calendar = NSCalendar.currentCalendar() // Set up date object let 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 month let components = NSCalendar.currentCalendar().components(NSCalendarUnit.CalendarUnitMonth, fromDate: date) components.month // Getting the First and Last date of the month components.day = 1 let firstDateOfMonth: NSDate = calendar.dateFromComponents(components)! components.month  += 1 components.day     = 0 let lastDateOfMonth: NSDate = calendar.dateFromComponents(components)! var unitFlags = NSCalendarUnit.WeekOfMonthCalendarUnit |  NSCalendarUnit.WeekdayCalendarUnit     |  NSCalendarUnit.CalendarUnitDay let firstDateComponents = calendar.components(unitFlags, fromDate: firstDateOfMonth) let lastDateComponents  = calendar.components(unitFlags, fromDate: lastDateOfMonth) // Sun = 1, Sat = 7 let firstWeek = firstDateComponents.weekOfMonth let lastWeek  = lastDateComponents.weekOfMonth let numOfDatesToPrepend = firstDateComponents.weekday - 1 let numOfDatesToAppend  = 7 - lastDateComponents.weekday + (6 - lastDateComponents.weekOfMonth) * 7 let 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: $0, toDate: startDate, options: nil)! }) "/(components.year)" var dateString = "2014-10-3" // change to your date format var dateFormatter = NSDateFormatter() dateFormatter.dateFormat = "YYYY-MM-dd" var someDate = dateFormatter.dateFromString(dateString) println(someDate)

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