I have an array of string but would like to change the order that they show depending on user input.

//Array of day
let days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
// User input
let startDayOfWeek = 1

var startOfWeek: [String] {
    guard startDayOfWeek != 0 else { return days }
    var newDays = [String]()

    for i in startDayOfWeek..<days.count {
        newDays.append(days[i])
    }

    for i in 0..<startDayOfWeek {
        newDays.append(days[i])
    }

    return newDays
}

print(startOfWeek)

Is there a better way to do this?

maybe as simple as this...

enum StartOfWeek {
    case sun
    case mon
}

var startOfWeek = StartOfWeek.mon
var weekDays: [String] = []

switch startOfWeek {
case .sun:
    weekDays = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
case .mon:
    weekDays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
}

or like this

enum StartOfWeek {
    case sun
    case mon
}

var days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]

var startOfWeek = StartOfWeek.sun

switch startOfWeek {
case .sun:
    days
case .mon:
    days = Array(days.dropFirst())
    days.append("Sun")
}

or that )))

enum StartOfWeek {
    case sun
    case mon
}

var days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]

var startOfWeek = StartOfWeek.mon

switch startOfWeek {
case .sun:
    days
case .mon:
    let day = days.removeFirst()
    days.append(day)
}

but I think this is more readable )))

enum StartOfWeek {
    case sun
    case mon
}

let sunday = "Sun"
var days = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]

var startOfWeek = StartOfWeek.sun

switch startOfWeek {
case .sun:
    days.insert(sunday, at: 0)
case .mon:
    days.append(sunday)
}

hi,

i took Nigel's question to be a more general one of rotation, not just whether the startOfWeek is 0 or 1. e.g., a business might be closed on Sunday and Monday, so people working there might treat their weekdays as Tuesday through Saturday.

this would work:

var startOfWeek: [String] {
    let startIndex = max(startDayOfWeek, 0) % 7 // startIndex >= 0 and values 7 + higher ==> start counting again at "Sun"
    let daysStartingAt = days.dropFirst(startIndex) + days.dropLast(7 - startIndex)
    return(Array(daysStartingAt))
}

you can also find a rotate function defined on BidirectionalCollection in the Algorithms package. that would look like this

import Algorithms

// other stuff ...

var startOfWeek: [String] {
    let startIndex = max(startDayOfWeek, 0) % 7 // values 7 + higher ==> start counting again at "Sun"
    var normalDays = days // makes a copy
    normalDays.rotate(toStartAt: startIndex)// rotates in place
    return normalDays
}

hope that's of interest,

DMG

Thank you for your replys. Yes it a calendar and would like the option to pick the start day of week (this can be any day not just Sunday or Monday). I choose Int as when working out all the days from a selected Date it will then work out the first weekday of month, using

let firstDayOfWeek = calendar.component(.weekday, from: startOfMonth)

So firstDayOfWeek match the order in the array however if I change the order then will need to adjust the startDayOfWeek.

If you want to see that code I can show it to you.