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

Question

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

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

Anyone have any idea/info about this update?

Solution 1

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

Solution 2

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

Solution 3

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

Solution 4

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

Solution 5

Just remove characters For example:

stringValue.characters.count to stringValue.count

View more solutions

Comments

[vadian]

Here is an interesting article about the String changes from Swift 3 to 4 and please read also SE0163

[holex]

try to use count instead.

[Efren]

If you were using string.characters.forEach the new API is string.forEach { char in process(char) }

[Krunal]

Thanks for your answer.. But can I have detail reference of sub string. This is just sample example, I've so many other operations dealing with characters

[songxunzhao]

Please check detail information from here. developer.apple.com/library/content/documentation/Swift/…

[songxunzhao]

let greeting = "Hello, world!" let index = greeting.index(of: ",") ?? greeting.endIndex let beginning = greeting[..<index]

[Dennis Vennink]

Online reference for Substring.

[Leo Dabus]

Never use count > 0 to check if a collection is empty. There is a property on Collection called isEmpty exactly for that. From the docs When you need to check whether your collection is empty, use the isEmpty property instead of checking that the count property is equal to zero. For collections that don’t conform to RandomAccessCollection, accessing the count property iterates through the elements of the collection.

[Jonny]

extension Collection {var isNotEmpty: Bool {get {return self.isEmpty ? false : true}}}

[Bhanu Birani]

Is it backward compatible? I've few 3.0.2 version to support as well.

[Leo Dabus]

@Jonny extension Collection { var isNotEmpty: Bool { return !isEmpty } }

[Pulkit]

I want to get first character of string so I want to know that which way should I use let firstElement = spString.first or Substring?

[Pranavan SP]

@Pulkit Better to use .first because if string is "" empty. it will only return nil but substring will produce error.

[Pulkit]

how to convert this line of code to swift 4 'AuthorImageText = String(val.characters[(AuthorName.startIndex)]).capitalized'

[Pranavan SP]

@Pulkit just remove .characters enough

[Timothy Kanski]

This should be the accepted answer. The question is about the replacement for string.characters.count, not the replacement for comparing to zero; that's only mentioned in the screenshot.