如何在Swift中更改星期的第一天

Question

I have made a functioning app and part of it includes formatting the date from a date picker.

I need to change the first day of the week as the week days are being displayed as "1" - "7". However, day 1 is currently Sunday and I need day 1 to be Monday and Sunday as day 7.

The code for my date formatter and picker are below:

var chosenDate = self.datePicker.date
var formatter = NSDateFormatter()        
formatter.dateFormat = "ewYY"

let day = formatter.stringFromDate(chosenDate)
let dateResult = "\(day)"

DestViewController.date = dateResult

I got all of my date formatting info from this page:

http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Format_Patterns

I just can't seem to work out how to change this first day of the week?

Many thanks in advance Mark.

Answer 1

Here is good example in how to manipulate date in swift. you can change the code to fit it better for what you may need, but right now it does what you need.

// Playground - noun: a place where people can play

// 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 = 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 = stringFromDate(NSDate())// change to your date format
var dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "EE"
var dateString = dateFormatter.stringFromDate(NSDate())
var xdate = dateFormatter.dateFromString(dateString)
//var someDate = dateFormatter.dateString
println(dateString)

this will output::

"Thu"