'subscript' is unavailable: cannot subscript String with a CountableClosedRange, see the documentation comment for discussion

Question

In Swift 4, I\'m getting this error when I try to take a Substring of a String using subscript syntax.

\'subscript\' is unavaila

Answer 1

1. How can I resolve this error?

This error means you can't use an Int in the subscript format – you have to use a String.Index, which you can initialize with an encodedOffset Int.

let myString: String = "foobar"
let lowerBound = String.Index.init(encodedOffset: 1)
let upperBound = String.Index.init(encodedOffset: 3)
let mySubstring: Substring = myString[lowerBound..

2. Where is "the documentation comment for discussion" that was referred to in the error?

It's on GitHub in the Swift Standard Library repository in a file called UnavailableStringAPIs.swift.gyb in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying 'Beware of the Leopard'. link