Check if string contains special characters in Swift

Question

I have to detect whether a string contains any special characters. How can I check it? Does Swift support regular expressions?

var characterSet:NSCharacterSet = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
if (searchTerm!.rangeOfCharacterFromSet(characterSet).location == NSNotFound){
    println("Could not handle special characters")
}

I tried the code above, but it matches only if I enter the first character as a special character.

I don't think it really matters, but warning to others: the string in this question with all the letters & numbers has an extra 'K' (...JKLKM...). That extra K has propagated through the 4 answers below that also use the string. — Dan Jackson, Apr 07 '17 at 08:31

Martin R · Accepted Answer · 2017-04-11T03:26:42.570

99

Your code check if no character in the string is from the given set. What you want is to check if any character is not in the given set:

if (searchTerm!.rangeOfCharacterFromSet(characterSet.invertedSet).location != NSNotFound){
    println("Could not handle special characters")
}

You can also achieve this using regular expressions:

let regex = NSRegularExpression(pattern: ".*[^A-Za-z0-9].*", options: nil, error: nil)!
if regex.firstMatchInString(searchTerm!, options: nil, range: NSMakeRange(0, searchTerm!.length)) != nil {
    println("could not handle special characters")

}

The pattern [^A-Za-z0-9] matches a character which is not from the ranges A-Z, a-z, or 0-9.

Update for Swift 2:

let searchTerm = "a+b"

let characterset = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
if searchTerm.rangeOfCharacterFromSet(characterset.invertedSet) != nil {
    print("string contains special characters")
}

Update for Swift 3:

let characterset = CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
if searchTerm.rangeOfCharacter(from: characterset.inverted) != nil {
    print("string contains special characters")
}

edited Apr 11 '17 at 03:26

answered Dec 30 '14 at 09:50

Martin R

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Thanks for point out. Is it possible to achieve this using Regular expression? – iPhone Guy Dec 30 '14 at 10:07
Thank you for the answer. – iPhone Guy Dec 30 '14 at 14:12
2

But what about other languages? – nikolsky Aug 10 '16 at 04:50
7

@nikolsky: You can use `NSCharacterSet.alphanumericCharacterSet()` to cover alphanumeric characters from all languages. – Martin R Aug 10 '16 at 05:20
1

@MartinR thank you. alphanumericCharacterSet() is definitely more universal then using charactersInString: – nikolsky Aug 10 '16 at 05:27
@nikolsky: Yes, but it depends on the application. There may be cases where you only "english" letters and digits are allowed, e.g. for part numbers in an order system. For user names you'll want to allow "international" letters. – Martin R Aug 10 '16 at 05:40
FYI: There is a stray "K" in the capital letters list for both sets. I cannot edit this since it doesn't change 6 or more characters.. – Matt Butler Apr 11 '17 at 01:18
@MartinR why is there inverted? Is this neccessary? – Evgeniy Kleban Jan 27 '18 at 22:40
@EvgeniyKleban: Yes, because the question was to check if the string contains any special characters. Without inverting the characterset we would test if the string contains any alphanumeric character. – Martin R Jan 27 '18 at 22:58
how to check with multiple languages? do i have to add other language char in the given characterset ? – souvickcse Aug 27 '19 at 09:27
How about numbers? I want to take them out, but to be able to use all languages? – Vladimir Sukanica Aug 21 '20 at 05:52

score 10 · Answer 2 · answered May 23 '18 at 07:36

This answer may help the people who are using Swift 4.1

func hasSpecialCharacters() -> Bool {

    do {
        let regex = try NSRegularExpression(pattern: ".*[^A-Za-z0-9].*", options: .caseInsensitive)
        if let _ = regex.firstMatch(in: self, options: NSRegularExpression.MatchingOptions.reportCompletion, range: NSMakeRange(0, self.count)) {
            return true
        }

    } catch {
        debugPrint(error.localizedDescription)
        return false
    }

    return false
}

Taken reference from @Martin R's answer.

score 6 · Answer 3 · answered Oct 23 '19 at 18:31

6

With Swift 5 you can just do

if let hasSpecialCharacters =  "your string".range(of: ".*[^A-Za-z0-9].*", options: .regularExpression) != nil {}

answered Oct 23 '19 at 18:31

Ali

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score 5 · Answer 4 · edited Nov 09 '20 at 19:43

5

Inverting your character set will work, because in your character set you have all the valid characters:

var characterSet:NSCharacterSet = NSCharacterSet(charactersInString: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
if (searchTerm!.rangeOfCharacterFromSet(characterSet.invertedSet).location == NSNotFound){
    println("No special characters")
}

Hope this helps.. :)

edited Nov 09 '20 at 19:43

pkamb

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answered Dec 30 '14 at 09:52

Rashad

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Your check is the wrong way around. *"Could not handle special characters"* is printed if the string contains *no* special characters. – Martin R Dec 30 '14 at 09:57
Now it is correct (and equivalent to the code in my answer, which for some reason was downvoted :) – Martin R Dec 30 '14 at 10:01
@MartinR> I don't know. but yes yours and my solution is same. You got 2 upvotes though. :P – Rashad Dec 30 '14 at 10:02
Thanks for pointing out.Is it possible to achieve this using Regular expression? – iPhone Guy Dec 30 '14 at 10:08

score 5 · Answer 5 · answered Jan 16 '18 at 13:30

Password validation With following:- (Password at least eight characters long, one special character, one uppercase, one lower case letter and one digit)

var isValidateSecialPassword : Bool {

        if(self.count>=8 && self.count<=20){
        }else{
            return false
        }
        let nonUpperCase = CharacterSet(charactersIn: "ABCDEFGHIJKLMNOPQRSTUVWXYZ").inverted
        let letters = self.components(separatedBy: nonUpperCase)
        let strUpper: String = letters.joined()

        let smallLetterRegEx  = ".*[a-z]+.*"
        let samlltest = NSPredicate(format:"SELF MATCHES %@", smallLetterRegEx)
        let smallresult = samlltest.evaluate(with: self)

        let numberRegEx  = ".*[0-9]+.*"
        let numbertest = NSPredicate(format:"SELF MATCHES %@", numberRegEx)
        let numberresult = numbertest.evaluate(with: self)

        let regex = try! NSRegularExpression(pattern: ".*[^A-Za-z0-9].*", options: NSRegularExpression.Options())
        var isSpecial :Bool = false
        if regex.firstMatch(in: self, options: NSRegularExpression.MatchingOptions(), range:NSMakeRange(0, self.count)) != nil {
            print("could not handle special characters")
            isSpecial = true
        }else{
            isSpecial = false
        }
        return (strUpper.count >= 1) && smallresult && numberresult && isSpecial
    }

score 3 · Answer 6 · answered Nov 20 '15 at 10:28

@Martin R answer is great, I just wanted to update it (the second part) to Swift 2.1 version

let regex = try! NSRegularExpression(pattern: ".*[^A-Za-z0-9].*", options: NSRegularExpressionOptions())
if regex.firstMatchInString(searchTerm!, options: NSMatchingOptions(), range:NSMakeRange(0, searchTerm!.characters.count)) != nil {
    print("could not handle special characters")
}

I used try! as we can be sure it create a regex, it doesn't base on any dynamic kind of a data

score 2 · Answer 7 · edited Nov 09 '20 at 19:43

2

Depending on the definition of special characters, you could use this:

let chars =  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

chars.canBeConvertedToEncoding(NSASCIIStringEncoding)

edited Nov 09 '20 at 19:43

pkamb

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answered Jun 09 '16 at 18:46

MirekE

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score 1 · Answer 8 · edited Nov 09 '20 at 19:44

Two Solutions:

1)

extension String {
    var stripped: String {
        let okayChars = Set("abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ")
        return self.filter {okayChars.contains($0) }
    }
}

2)

class TrimDictionary {

    static func trimmedWord(wordString: String) -> String {
        var selectedString = wordString
    
        let strFirst = selectedString.first
        let strLast = selectedString.last
    
        let characterset = CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
        if strFirst?.description.rangeOfCharacter(from: characterset.inverted) != nil {
            selectedString = String(selectedString.dropFirst())
        }
        if strLast?.description.rangeOfCharacter(from: characterset.inverted) != nil {
            selectedString = String(selectedString.dropLast())
        }
        return selectedString
    }
}

score 1 · Answer 9 · answered Oct 18 '19 at 07:53

For the purpose of filename sanitization, I prefer to detect the invalid characters, rather than provide an allowed character set. After all, many non-English speaking users need accented characters. The following function is inspired by this gist:

func checkForIllegalCharacters(string: String) -> Bool {
    let invalidCharacters = CharacterSet(charactersIn: "\\/:*?\"<>|")
    .union(.newlines)
    .union(.illegalCharacters)
    .union(.controlCharacters)

    if string.rangeOfCharacter(from: invalidCharacters) != nil {
        print ("Illegal characters detected in file name")
        // Raise an alert here
        return true
    } else {
    return false
}

score 0 · Answer 10 · answered Sep 20 '19 at 14:34

Mahendra's answer can be stripped down a bit by using an inversion(^) within the regex clause. Additionally, you don't need A-Z and a-z when using the caseInsensitive option, as Swift covers that eventuality for you:

extension String {

  func containsSpecialCharacters(string: String) -> Bool {
        
        do {
            let regex = try NSRegularExpression(pattern: "[^a-z0-9 ]", options: .caseInsensitive)
            if let _ = regex.firstMatch(in: string, options: [], range: NSMakeRange(0, string.count)) {
                return true
            } else {
                return false
            }
        } catch {
            debugPrint(error.localizedDescription)
            return true
        }
    }

Check if string contains special characters in Swift

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