add a range of objects from one array to another

Question

Currently we have 2 arrays:

  fileprivate var totalDrinksArray: [CocktailModel] = []
  fileprivate var currentDrinksArray: [CocktailModel] = []

What I'm trying to do is get the first 2 objects of the totalDrinksArray and add them to the currentDrinksArray . After a button is pressed the next 2 drinks will be added from the totalDrinksArray to the currentDrinksArray (for a total of 4 drinks )and so on.

Answer 1

You can "add" arrays together:

currentDrinksArray += totalDrinksArray[0...1]

should work.

Not quite clear from your question, but if you want to "add the next two" (the 3rd and 4th):

currentDrinksArray += totalDrinksArray[2...3]

Answer 2

You can use Array method func prefix(_ maxLength: Int) which will return a slice of the total array (up to n elements) or less if there is not enough elements and append the contents to your current array or insert it at the desired index:

currentDrinksArray.append(contentsOf: totalDrinksArray.prefix(2))

Or if you would like to insert them in the beginning of your array:

currentDrinksArray.insert(contentsOf: totalDrinksArray.prefix(2), at: 0)

Answer 3

Simplest safe solution IMO:

var currentIndex = 0
func addDrinks() {
    if(currentIndex + 2 >= totalDrinksArray.count) {
        currentDrinksArray += totalDrinksArray[currentIndex...]
    }
    else {
        currentDrinksArray += totalDrinksArray[currentIndex..<(currentIndex + 2)]
    }
    currentIndex += 2
}