warning: 'characters' is deprecated: Please use String or Substring directly

user_5638630 0
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characters - an instance property of String, is deprecated from with Xcode 9.1

It was very useful to get a substring from String by using the characters property but now it has been deprecated and Xcode suggests to use substring. I've tried to check around SO questions and apple developer tutorials/guidelines for the same. But could not see any solution/alternate as suggested.

Here is warning message:

'characters' is deprecated: Please use String or Substring

enter image description here

I've so many string operations are performed/handled using property characters.

Anyone have any idea/info about this update?

xcode9.1 swift4 substring ios string
8 Answers

Swift 4 introduced changes on string API.
You can just use !stringValue.isEmpty instead of stringValue.characters.count > 0

for more information you get the sample from here

for e.g 

let edit = "Summary"
edit.count   // 7
user_68798700

Swift 4 vs Swift 3 examples:

let myString = "test"

for char in myString.characters {print(char) } // Swift 3
for char in myString { print(char) } // Swift 4

let length = myString.characters.count // Swift 3
let length = myString.count // Swift 4
user_73655450

One of the most common cases for manipulating strings is with JSON responses. In this example I created an extension in my watch app to drop the last (n) characters of a Bitcoin JSON object.

Swift 3:

func dropLast(_ n: Int = 0) -> String {
    return String(characters.dropLast(n))

Xcode 9.1 Error Message:

'characters' is deprecated: Please use String or Substring directly

Xcode is telling us to use the string variable or method directly.

Swift 4:

func dropLast(_ n: Int = 0) -> String {
    return String(dropLast(n))
    }

Complete Extension:

extension String {
    func dropLast(_ n: Int = 0) -> String {
        return String(dropLast(n))
    }

    var dropLast: String {
        return dropLast()
    }
}

Call:

print("rate:\(response.USDRate)")
let literalMarketPrice = response.USDRate.dropLast(2)
print("literal market price: \(literalMarketPrice)")

Console:

//rate:7,101.0888 //JSON float
//literal market price: 7,101.08 // JSON string literal

Additional Examples:

  • print("Spell has \(invisibleSpellName.count) characters.")
  • return String(dropLast(n))
  • return String(removeLast(n))

Documentation:

You'll often be using common methods such as dropLast() or removeLast() or count so here is the explicit Apple documentation for each method.

droplast()

removelast()

counting characters

user_41559760

Use this characters because String stopped being a collection in Swift 2.0. However this is still valid code in Swift 4 but is no longer necessary now that String is a Collection again.

For example a Swift 4 String now has a direct count property that gives the character count:

// Swift 4
let spString = "Stack"
spString.count           // 5

Examples for String and SubString.

String

Swift 4 String now directly get Element that gives the first character of String: (string.characters.first)

let spString = "Stack"
let firstElement = spString.first   //S

SubString

Using SubString get first character. 

let spstring = "Welcome"
let indexStartOfText = spstring.index(spstring.startIndex, offsetBy: 1)
let sub = spstring.substring(to: indexStartOfText)
print(sub) //W
user_83689820
user_29153630

Just remove characters For example:

stringValue.characters.count to stringValue.count

user_97821840

You can also use this code for dictionary grouping without using { $0.characters.first! }. 

let cities = ["Shanghai": 24_256_800, "Karachi": 23_500_000, "Beijing": 21_516_000, "Seoul": 9_995_000]
let groupedCities = Dictionary(grouping: cities.keys) { $0.first! }
print(groupedCities)
user_44769890 
func validatePhoneNumber(number:String) -> Bool{
    if number.count < 10. //deprecated ->(number.characters.count)
    {
        return false;
    }else{
        return true;
    }
}

You use directly .count and characters is deprecated.

user_142151430
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