How can I check is there any consecutive characters with a regex in Swift 4.0?

Question

Can anyone give me a Swift regex to identify consecutive characters in a string?

My regex is .*(.)\\1$ and this is not working. My code block is;

let regex = ".*(.)\\1$"
return NSPredicate(format: "SELF MATCHES %@", regex).evaluate(with: string)

Examples:

abc123abc -> should be valid

abc11qwe or aa12345 -> should not be valid because of 11 and aa

Thanks

`.*(.)\\1$` will only get repeated characters at the end of a string because you anchored it with `$`. You haven't given us sample strings so there isn't much we can say as to why this isn't working since we don't have sample input to test against. Are you simply checking whether or not a single repeated character exists? — ctwheels, Apr 10 '18 at 13:50
@ctwheels, i edit the question and add some examples. Thanks — AykutE, Apr 10 '18 at 13:55
@aykutt you can simply use `(.)\\1`. Is this for password validation by chance? — ctwheels, Apr 10 '18 at 13:56
If you want to use `NSPredicate` with `MATCHES` you need `let regex = ".*(.)\\1.*$"`, but it is very inefficient. — Wiktor Stribiżew, Apr 10 '18 at 14:11
@aykutt this may help you then: [Reference - Password Validation](https://stackoverflow.com/questions/48345922/reference-password-validation/) — ctwheels, Apr 10 '18 at 14:14
If you really want to use a regex, you'd better use partial matching, something like `if let range = str.range(of: "(.)\\1", options: .regularExpression) { ... }` — Wiktor Stribiżew, Apr 10 '18 at 14:27

Krunal · Accepted Answer · 2018-04-10T14:37:34.747

This regex may help you, (Identifies consecutive repeating characters - It validates and satisfies matches with samples you've shared. But you need to test other possible scenarios for input string.)

(.)\\1

Try this and see:

let string = "aabc1123abc"
//let string = "abc123abc"
let regex = "(.)\\1"
if let range = string.range(of: regex, options: .regularExpression) {
    print("range - \(range)")
}

// or

if string.range(of: regex, options: .regularExpression) != nil {
    print("found consecutive characters")
}

Result:

score 2 · Answer 2 · answered Apr 10 '18 at 14:28

Use NSRegularExpression instead of NSPredicate

let arrayOfStrings = ["abc11qwe","asdfghjk"]
for string in arrayOfStrings {
        var result = false
        do{
            let regex = try NSRegularExpression(pattern: "(.)\\1", options:[.dotMatchesLineSeparators]).firstMatch(in: string, range: NSMakeRange(0,string.utf16.count))
            if((regex) != nil){
                result = true
            }

        }
        catch {

        }
        debugPrint(result)
    }

How can I check is there any consecutive characters with a regex in Swift 4.0?

2 Answers2