How can I print a new array element every day? - ios

Question

I'm trying to pick a new element of my array every day starting at midnight, and then once all elements have been used, jump back to the start of the array. What would be the best way to do so? Here's what I have so far.
import UIKit
var wordsArray = [String] ()
wordsArray = ["Hallo","Apfel","Geburtstag","Pherd","Angst"]
let date = NSDate ()
let calendar:NSCalendar! = NSCalendar(calendarIdentifier: NSCalendar.Identifier.gregorian)
var dateComponents = DateComponents()
dateComponents.day = 1
while wordsArray (0..<2) {
gregorian.date(byAdding: NSCalendar.Unit.day, value: $0, to: now, options: NSCalendar.Options(rawValue: 0))
}

Answer 1

If I understand you right, you want to use a certain array element every day, and these elements should be chosen cyclically.
So the main problem is how to do something every day at midnight.
This can be achieved using a Timer:
// First determine coming midnight
let calendar = NSCalendar.current
let nextDay = calendar.date(byAdding: .day, value: 1, to: Date())
let comingMidnight = calendar.startOfDay(for: nextDay!)
// Then start a time coming midnight, and repeat it every day
// Please note that 24 * 60 * 60 is not completely correct considering daylight saving times
// Sometimes days have 23 hours and sometimes 25 hours!
_ = Timer.init(fireAt: comingMidnight, interval: 24 * 60 * 60, target: self, selector: Selector(("timerFired")), userInfo: nil, repeats: true)
// And this is the timer callback:
func timerFired(timer: Timer) {
// Here you can select the next element in your array, any do what is required
// For selecting the elements cyclically, see the other answers!
}
This code has not been tested, but it should give you an idea how to proceed.

Answer 2

To wrap around the array use the modulo operator, it devides index / number of items in the array and returns the remainder of the division – in this case always 0...4
let wordsArray = ["Hallo","Apfel","Geburtstag","Pferd","Angst"]
for i in 0..<10 {
print(wordsArray[i % wordsArray.count])
}
Create an index variable in your code
var index = 0
and increment it this way
index = (index + 1) % wordsArray.count

Answer 3

This is the easiest way I could think of.
var wordsArray = [String] ()
wordsArray = ["Hallo","Apfel","Geburtstag","Pherd","Angst"]
let secondsInDay = (60 * 60 * 24)
let dayNumber = Int(NSDate().timeIntervalSince1970 / Double(secondsInDay))
let selectedNumber = dayNumber % wordsArray.count
let chosenWord = wordsArray[selectedNumber]
print(chosenWord)
EDIT: another method hopefully satisfying a complaint
var wordsArray = [String] ()
wordsArray = ["Hallo","Apfel","Geburtstag","Pherd","Angst"]
let calendar = Calendar(identifier: .gregorian)
let date = Date()
let yearNumber = calendar.component(.year, from: date)
let monthNumber = calendar.component(.month, from: date)
let dayNumber = calendar.component(.day, from: date)
let daysInYear = Double(yearNumber) * 12.0 * 365.25
let daysInMonth = Double(monthNumber) * 30.42
let totalNumber = daysInYear + daysInMonth + Double(dayNumber)
let selectedNumber = Int(totalNumber) % wordsArray.count
let chosenWord = wordsArray[selectedNumber]
print(chosenWord)