'substring(to:)' is deprecated: Please use String slicing subscript with a 'partial range upto' operator

Question

How can I update the following code to the new version of swift:

self.areaCodeLael.text! = localNumber.substring(to: localNumber.index(localNumber.startIndex, offsetBy: 3))

I have tried following this post but I can't get it right How can I use String slicing subscripts in Swift 4?

I adjusted my original code to localNumber[..<3] but I get:

Cannot subscript a value of type 'String' with an index of type 'PartialRangeUpTo'

Update your question showing how you attempted to make use of the information in the linked question. — rmaddy, Aug 28 '17 at 15:51
Unrelated but why are you putting the `!` operator just before the `=`? Get rid of that. — rmaddy, Aug 28 '17 at 15:52

score 19 · Accepted Answer · answered Aug 28 '17 at 15:53

19

I would say localNumber.prefix(3) in this situation. Short and sweet.

answered Aug 28 '17 at 15:53

matt

I tried that but prefix is an unresolved identifier localNumber.String(prefix(3)) – user1079052 Aug 28 '17 at 16:00
I got it to work, thank you for the suggestion String(localNumber.characters.prefix(3)) – user1079052 Aug 28 '17 at 16:04
2

@user1079052 No, you want `String(localNumber.prefix(3))`. – rmaddy Aug 28 '17 at 16:05
I wrapped it in String(). Thanks! – user1079052 Aug 29 '17 at 16:42

score 8 · Answer 2 · answered Aug 28 '17 at 16:08

8

The problem with your attempt to use localNumber[..<3] is that you can't pass an Int as the range. You need to pass a String.Index.

Your code needs to be:

let index = localNumber.index(localNumber.startIndex, offsetBy: 3)
self.areaCodeLael.text = localNumber[..<index]

Also note that you do not want the ! operator after text.

answered Aug 28 '17 at 16:08

rmaddy

I get "_Cannot subscript a value of type 'String' with an index of type 'PartialRangeUpTo'_" – Cœur Jan 03 '18 at 05:24
Oh, I solve it by wrapping the subscript result with `String( … )`, like `String(localNumber[.. – Cœur Jan 03 '18 at 05:31

2 Answers2