How can I check to see if a string contains characters of whitespace/alphanumeric/etc?

Question

How can you use the "ctype.h" library in Swift to be able to use isAlpha or isSpace on characters? Or is there a better, Swift, way of doing it?

This question is answered, but it doesn't seem to work: Swift: how to find out if letter is Alphanumeric or Digit

It doesn't specify how to import the library. Could someone point me in the right direction?

Here's what I've got so far:

extension String {
    subscript (i : Int) -> String {
        return String(Array(self)[i])
    }
}

let whitespace = NSCharacterSet.whitespaceCharacterSet()

let phrase = "Test case"

for var i=0; i<countElements(phrase); i++ {
    if whitespace.characterIsMember(phrase[i]) { //error
        println("char is whitespace")
    }
}

Is it a good idea to use methods that don't support Unicode on Swift strings? — trojanfoe, Jul 22 '14 at 09:54
It seems that the (ASCII-only) functions isAlpha(), isDigit() have been removed from Swift. But the NSCharacterSet-based method from that answer should still work. — Martin R, Jul 22 '14 at 09:59
I'm trying to use that (NSCharacterSet), but it keeps saying "character is not convertible to unichar". — hazrpg, Jul 22 '14 at 10:03
Post your code. Remember how Swift handles automatic conversions between different primitive types? — gnasher729, Jul 22 '14 at 10:11

score 35 · Accepted Answer · answered Jul 22 '14 at 12:09

Use NSCharacter on the entire string,not character-by-character:

let whitespace = NSCharacterSet.whitespaceCharacterSet()

let phrase = "Test case"
let range = phrase.rangeOfCharacterFromSet(whitespace)

// range will be nil if no whitespace is found
if let test = range {
    println("whitespace found")
}
else {
    println("whitespace not found")
}

Output:

whitespace found

score 11 · Answer 2 · edited May 27 '20 at 14:44

11

I created a String extension that does exactly this, hope it's useful.

extension String {
    func containsWhitespaceAndNewlines() -> Bool {
        return rangeOfCharacter(from: .whitespacesAndNewlines) != nil
    }
}

// Usage
"hello, world!".containsWhitespaceAndNewlines() // true
"hello,world!".containsWhitespaceAndNewlines() // false

edited May 27 '20 at 14:44

Islam

3,654
3
30
40

answered Nov 17 '15 at 15:26

Samuel B.

363
1
4
10

Rick Pasveer · Answer 3 · 2018-04-09T14:21:33.593

10

Shorter extension (swift 4.1)

extension String {
    var containsWhitespace : Bool {
        return(self.rangeOfCharacter(from: .whitespacesAndNewlines) != nil)
    }
}

You can change the .whitespacesAndNewlines with any other CharacterSet like this:

extension String {
    var containsDigits : Bool {
        return(self.rangeOfCharacter(from: CharacterSet.decimalDigits) != nil)
    }
}

edited Apr 09 '18 at 14:21

answered Mar 27 '17 at 12:57

Rick Pasveer

480
7
12

score 2 · Answer 4 · answered Mar 10 '19 at 19:42

This answer works with text fields. I was going crazy trying to search for whitespace on a UItextfield without searching the string content of it. This works for UItextfields:

Swift 4:

    if (textField.text?.contains(" "))!{
        print("Has space")
    }else{
        print("Does not have space")
    }

This is for a regular string, also in swift 4

    if string.contains(" "){
        print("Has space")
    }else{
        print("Does not have space")
    }

score 1 · Answer 5 · answered Sep 07 '19 at 22:15

For Swift 5

extension String {

    func containsWhiteSpace() -> Bool {

        // check if there's a range for a whitespace
        let range = self.rangeOfCharacter(from: .whitespacesAndNewlines)

        // returns false when there's no range for whitespace
        if let _ = range {
            return true
        } else {
            return false
        }
    }
}

score -1 · Answer 6 · edited Aug 30 '21 at 12:30

This function will tell you if there is a whitespace between a string. for example if you are trying to make sure the user enter a first and last name

Swift 5

func validatTextField() -> Bool {
        var isValid = false
        if textField.text!.contains(" ") && !textField.text!.isEmpty{
            let cardHolderChar = textField.text!
            for i in cardHolderChar {
                if i == " " && i == cardHolderChar.last {
                    isValid = false
                }
                else {
                    isValid = true
                }
            }
        }
        return isValid
    }

How does this answer the question? You haven't provided any comment — Marek H, Aug 28 '21 at 21:28

How can I check to see if a string contains characters of whitespace/alphanumeric/etc?

6 Answers6

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