Array with multiple values per index?

Question

I'm learning swift, and I do the sololearn course to get some knowledge, but I bumped into something that I don't understand.
It is about modifying an array's values. The questionable part states the following:

In the following example, the elements with index 1, 2, 3 are replaced with two new values.

shoppingList[1...3] = [“Bananas”, “Oranges”]

How can an one dimensional array take more than one value per index? And how do I access them? Am I misunderstanding something?

Use Tuple for each index. https://stackoverflow.com/a/25838682/14733292 — Raja Kishan, May 13 '21 at 18:22
What the code above does is the same as `replaceSubrange` method where you replace any number of elements with another collection. — Leo Dabus, May 13 '21 at 18:26

score 3 · Answer 1 · answered May 13 '21 at 19:01

When you assign to a range of indices in an array (array[1...3]), those elements are removed from the array and the new elements are 'slotted in' in their place. This can result in the array growing or shrinking.

var array = Array(0...5)
// [0, 1, 2, 3, 4, 5]
array[1...3] = [-1, -2]
// [0, -1, -2, 3, 4]

Notice how our array's length is now one element shorter.

score 3 · Accepted Answer · answered May 13 '21 at 19:55

3

What this code does is replacing the element of shoppingList in the 1...3 range using Array.subscript(_:)

That means considering this array:

var shoppingList = ["Apples", "Strawberries", "Pears", "Pineaples"]

that with:

shoppingList[1...3] = ["Bananas", "Oranges"]

Strawberries, Pears and Pineaples will be replaced by Bananas and Oranges.

so the resulting array will be: Apples, Bananas, Oranges

answered May 13 '21 at 19:55

AnderCover

2,488
3
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Thanks, this is exactly what I didn't understand! For some reason I thought that in the range from 1 to 3 every element would change to "bananas" and "oranges", so the array would have two values per index, and that got me confused. It is clear now! – Somee May 13 '21 at 20:11

score 0 · Answer 3 · answered May 13 '21 at 18:27

0

You could use a tuple (Value, Value), or create a struct to handle your values there, in fact if you plan to reuse this pair or value, a struct is the way to go.

By the way, there's no need to add [1..3], just put the values inside the brackets.

struct Value {
    var name: String
    var lastName: String
}

let values = [Value(name: "Mary", lastName: "Queen"), Value(name: "John", lastName: "Black")]

// Access to properties
let lastName = values[1].lastName

// OR

let tuples = [("Mary", "Queen"), ("John", "Black")]

let lastNameTuple = tuples[1].1

Hope you're enjoying Swift!

answered May 13 '21 at 18:27

Andy Nadal

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3
11

Thanks for your examples! But I'm still curious if the example given by SoloLearn makes any sense just by itself? – Somee May 13 '21 at 18:51
No need for any tuples, the code in the question works fine as it is. – Joakim Danielson May 13 '21 at 19:06

Array with multiple values per index?

3 Answers3