獲取沒有WeekCalendarUnit的星期的第一天

Question

我想根據NSDate得到一週的第一天。

它工作正常，但我有一個警告，因爲WeekCalendarUnit已棄用。

我做了一些研究，我試圖用更換WeekCalendarUnit：

static var CalendarUnitWeekday: NSCalendarUnit { get } 
static var CalendarUnitWeekdayOrdinal: NSCalendarUnit { get } 
static var CalendarUnitWeekOfMonth: NSCalendarUnit { get } 
static var CalendarUnitWeekOfYear: NSCalendarUnit { get } 

但我沒有得到相同的結果。這是我的垃圾代碼：

var date = NSDate() 
dateFormatter.dateFormat = "dd/YY" 
let calendar = NSCalendar.currentCalendar() 
let currentDateComponents = calendar.components(.CalendarUnitYear | .WeekCalendarUnit , fromDate: date) 
let startOfWeek = calendar.dateFromComponents(currentDateComponents) 
var dteString = dateFormatter.stringFromDate(startOfWeek!) 
// Output is "17/15" 

任何想法？

Answer 1

您可以結合使用.CalendarUnitWeekOfYear與 .CalendarUnitYearForWeekOfYear，這應該給預期的結果：

let currentDateComponents = calendar.components(.CalendarUnitYearForWeekOfYear | .CalendarUnitWeekOfYear , fromDate: date) 
let startOfWeek = calendar.dateFromComponents(currentDateComponents) 

另外，使用rangeOfUnit()（我個人覺得更容易 使用）：

var startOfWeek : NSDate? 
calendar.rangeOfUnit(.CalendarUnitWeekOfYear, startDate: &startOfWeek, interval: nil, forDate: date) 

在斯威夫特2這必須改爲

let currentDateComponents = calendar.components([.YearForWeekOfYear, .WeekOfYear ], fromDate: date) 
let startOfWeek = calendar.dateFromComponents(currentDateComponents) 

和

var startOfWeek : NSDate? 
calendar.rangeOfUnit(.WeekOfYear, startDate: &startOfWeek, interval: nil, forDate: date)