Using stringByReplacingCharactersInRange in Swift

Question

I'm trying to use UITextFieldDelegate in Swift/Xcode6 and I'm struggling with the way I'm supposed to use stringByReplacingCharactersInRange. The compiler error is 'Cannot convert the expression's type 'String' to type '$T8'.

func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool
{
    let s = textField.text.stringByReplacingCharactersInRange(range:range, withString:string)
    if countElements(s) > 0 {

    } else {

    }
    return true
}

Update for Xcode 6 Beta 5: The thing is shouldChangeCharactersInRange gives an NSRange object and we'd need a Swift Range object for stringByReplacingCharactersInRange. Can this still be considered a bug as I don't see why we should still be dealing with NS* objects? The String argument of the delegate method is anyway of a Swift type.

Nikolai Ruhe · Accepted Answer · 2017-01-18T10:53:30.947

34

Here's how to calculate the resulting string in various Swift versions.

Note that all methods use -[NSString stringByReplacingOccurrencesOfString:withString:] in exactly the same way, just differing in syntax.

This is the preferred way to calculate the resulting string. Converting to a Swift Range and use that on a Swift String is error prone. Johan's answer for example is incorrect in a couple of ways when operating on non-ASCII strings.

Swift 3:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let result = (textField.text as NSString?)?.replacingCharacters(in: range, with: string) ?? string
    // ... do something with `result`
}

Swift 2.1:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let result = (textField.text as NSString?)?.stringByReplacingCharactersInRange(range, withString: string)
    // ... do something with `result`
}

Swift 1 (only left here for reference):

let result = textField.text.bridgeToObjectiveC().stringByReplacingCharactersInRange(range, withString:string)

edited Jan 18 '17 at 10:53

answered Jun 03 '14 at 13:23

Nikolai Ruhe

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3

String has this method. See my comment. – Tomáš Linhart Jun 03 '14 at 13:33
@TomášLinhart Where does `String` declare this method? I can't find it in the Swift module. – Nikolai Ruhe Jun 03 '14 at 13:45
@NikolaiRuhe I don't know. But see my post and run in it in the playground and you will see it works. – Tomáš Linhart Jun 03 '14 at 13:46
iOS8 beta 5 compiler says: 'String' does not have a member names 'bridgeToObjectiveC' – János Aug 05 '14 at 12:14
3

At least as of Beta 5 this is no longer the correct answer. – Seppo Aug 07 '14 at 07:18
3

Use "textField.text as NSString" cast instead. – Zmey Aug 24 '14 at 20:37

score 17 · Answer 2 · edited Aug 19 '16 at 13:54

17

I created an extension to NSRange the converted to Range<String.Index>

extension NSRange {
    func toRange(string: String) -> Range<String.Index> {
        let startIndex = advance(string.startIndex, location)
        let endIndex = advance(startIndex, length)
        return startIndex..<endIndex
    }
}

So I can create the String like this

let text = textField.text
let newText = text.stringByReplacingCharactersInRange(range.toRange(text), withString: string)

in Swift 2.1 the extension looks like:

extension NSRange {
    func toRange(string: String) -> Range<String.Index> {
        let startIndex = string.startIndex.advancedBy(location)
        let endIndex = startIndex.advancedBy(length)
        return startIndex..<endIndex
    }
}

edited Aug 19 '16 at 13:54

Johan Kool

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answered Sep 12 '14 at 12:49

Johan

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Definitely the Swift-most answer in there. But you can avoid the `self`s :) – DeFrenZ Feb 27 '15 at 17:01
1

@DavideDeFranceschi I added the `self`s for clarity. But you are correct, they are not needed – Johan Mar 02 '15 at 14:17
1

That's a nice approach, but it breaks when you use unicode characters, such as emoji. Give it a try – Gui Moura Jun 30 '15 at 18:17
4

In Swift 2, you'd use `advancedBy`: `let startIndex = string.startIndex.advancedBy(location); let endIndex = startIndex.advancedBy(length)` – Rob Sep 27 '15 at 16:49
shouldn't the end index be advanced by `location + length` ? – Alnitak Mar 02 '16 at 14:17
There seems to be an error in the Swift 2.1 example of this solution. I think`let endIndex = string.startIndex.advancedBy(length)` should be `let endIndex = startIndex.advancedBy(length)` – Roel Spruit May 26 '16 at 08:38
@Joham correct let endIIndex = startIndex.advancedBy(length) – john07 Jul 02 '16 at 03:32
The approach in this answer is incorrect. You are using an NSString's character index for an indices on a Swift string's chracter view. These are not interchangeable. – Nikolai Ruhe Jan 18 '17 at 10:57

Sulthan · Answer 3 · 2014-06-03T15:49:53.963

15

The simplest solution I have found is using as NSString - that enables us to use NSRange.

var textField : UITextField = UITextField()
textField.text = "this is a test"

let nsRange : NSRange = NSRange(location: 0, length: 4)

let replaced = (textField.text as NSString)
               .stringByReplacingCharactersInRange(nsRange, withString: "that");

NSLog("Replaced: %@", replaced); //prints "that is a test"

edited Jun 03 '14 at 15:49

answered Jun 03 '14 at 15:02

Sulthan

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score 7 · Answer 4 · edited Nov 25 '14 at 03:31

7

let newString = (textField.text as NSString).stringByReplacingCharactersInRange(range, withString: string)

bridgeToObjectiveC can be removed in coming updates

edited Nov 25 '14 at 03:31

Adam Eberbach

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answered Nov 12 '14 at 11:16

Ankish Jain

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Short and sweet. As of swift2, textField.text needs force unwrapped: let newString = (textField.text! as NSString).stringByReplacingCharactersInRange(range, withString: string) – Eli Burke Dec 16 '15 at 21:43

score 6 · Answer 5 · answered Sep 16 '15 at 14:44

Nothing worked for me except the following: (FYI I'm using Xcode7.0 GM, Swift 2.0, iOS9GM)

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let currentText = textField.text ?? ""
    let prospectiveText = (currentText as NSString).stringByReplacingCharactersInRange(range, withString: string)
    print("prospectiveText", prospectiveText)
    return true;
}

score 3 · Answer 6 · answered Aug 14 '18 at 14:28

As of Swift 4, this is a little simpler, like Alexander Volkov's answer, but without the extension.

   func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let revisedText: String
        if let text = textField.text, let swiftRange = Range(range, in: text) {
            revisedText = text.replacingCharacters(in: swiftRange, with: string)
        } else {
            revisedText = string
        }
        // Do something with the text and return boolean.
   }

Change `let` to `var` to make `revisedText` mutable. – Jerrin Mar 09 '22 at 11:48 — Jerrin, Mar 09 '22 at 11:48

score 2 · Answer 7 · edited May 23 '17 at 12:03

This is a cross-post from this question, but without a way to make a Range<String.Index> the Swift-native String.stringByReplacingCharactersInRange() is pretty useless. So, here's a function to generate a Range<String.Index>:

func RangeMake(#start:Int, #end:Int) -> Range<String.Index> {
    assert(start <= end, "start must be less than or equal to end")
    func rep(str: String, count: Int) -> String {
        var result = ""
        for i in 0..count {
            result += str
        }
        return result
    }
    let length = end - start
    let padding = rep(" ", start)
    let dashes = rep("-", length)
    let search = padding + dashes
    return search.rangeOfString(dashes, options: nil, range: Range(start: search.startIndex, end: search.endIndex), locale: NSLocale.systemLocale())
}

let sourceString = "Call me Ishmael."
let range = RangeMake(start: 8, end: 15)    
let name = sourceString.substringWithRange(range)
// name = "Ishmael"

score 2 · Answer 8 · answered Mar 08 '18 at 18:15

Working & tested

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let newString = NSString(string: textField.text!).replacingCharacters(in: range, with: string)

    print(newString)

      return true;
}

score 1 · Answer 9 · answered Jun 03 '14 at 13:32

1

Creating String.Index is cumbersome.

let string = "hello"
let range = string.startIndex .. string.startIndex.succ().succ()
let result = string.stringByReplacingCharactersInRange(range, withString: "si")

answered Jun 03 '14 at 13:32

Tomáš Linhart

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I would post this as a bug. There should be a better way to create ranges of strings. Or maybe I just can't find it. – Sulthan Jun 03 '14 at 15:11
Feel free to report it. I also didn't find a better way. – Tomáš Linhart Jun 03 '14 at 16:33
I agree, my gut feeling was that this is a bug. For example stringByAppendingString works as expected. – Seppo Jun 03 '14 at 20:12

score 1 · Answer 10 · answered Jun 04 '15 at 06:28

for iOS 8.3 use following code

 func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool
{
    if textField.isEqual(<textField whose value to be copied>)
    {
        <TextField to be updated>.text = (textField.text as NSString).stringByReplacingCharactersInRange(range, withString: string)
    }

    return true
}

score 1 · Answer 11 · answered May 04 '16 at 14:51

With Swift 2.0, the answer from Durul must be changed because characters.count must be used instead of count().

The following must be done.

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let length = textField.text!.characters.count - range.length + string.characters.count
    if length > 0 {
        submitButton.enabled = true
    } else {
        submitButton.enabled = false
    }
    return true
}

score 0 · Answer 12 · answered Jul 22 '15 at 14:02

import UIKit

class LoginViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var submitButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }



    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        let length = count(textField.text) - range.length + count(string)
        if length > 0 {
            submitButton.enabled = true
        } else {
            submitButton.enabled = false
        }
        return true
    }
}

score 0 · Answer 13 · answered Feb 02 '18 at 11:38

Swift 4:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    var text = textField.text ?? ""
    text.replaceSubrange(range.toRange(string: text), with: string)
    ...
    return true
}

extension NSRange {

    /// Convert to Range for given string
    ///
    /// - Parameter string: the string
    /// - Returns: range
    func toRange(string: String) -> Range<String.Index> {
        let range = string.index(string.startIndex, offsetBy: self.lowerBound)..<string.index(string.startIndex, offsetBy: self.upperBound)
        return range
    }
}

When I delete one char I obtain a `Fatal error: Can't advance past endIndex` — Maximelc, Sep 24 '18 at 11:28
@Maximelc The suggested approach is correct. Provide your code. — Alexander Volkov, Oct 19 '18 at 15:20

Using stringByReplacingCharactersInRange in Swift

13 Answers13

Swift 3:

Swift 2.1:

Swift 1 (only left here for reference):

Linked

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