How can I truncate a String array in Swift?

Question

I have an array of strings in Swift that I want to shorten to only the first 5. It looks like I cannot do:

myArray = myArray[0..<5]

because I get a compiler error:

Cannot subscript a value of type [String] with an index of type Countable Range

So what can I do instead?

Show your actual code. `myArray[0..<5]` _is_ legal so you don't have what you think you have; this is probably an x-y problem, and we could get to the heart of it if you showed the real code. — matt, Aug 09 '17 at 17:38
while `myArray[0..<5]` may be legal, `array.prefix(n)` is a safer way since it is bounds safe! — Moriarty, Aug 09 '17 at 17:48

matt · Answer 1 · 2017-08-09T17:41:10.287

8

I would say

let arr2 = arr1.prefix(5)

Keep in mind that the result is a Slice. If you want an array, coerce back to an array. So e.g.

var arr1 = // ...
arr1 = Array(arr1.prefix(5))

However, the notation arr1[0..<5] is legal, though with the same proviso: it's a slice and would need to be cast back to an array in order to assign it where an array is expected.

edited Aug 09 '17 at 17:41

answered Aug 09 '17 at 17:35

matt

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score 3 · Answer 2 · answered Aug 09 '17 at 17:37

3

array = [1,2,3,4,5,6]
n = 5
array.prefix(n)

answered Aug 09 '17 at 17:37

Moriarty

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How can I truncate a String array in Swift?

2 Answers2