Using regex in Swift

Question

I'm trying to replace the occurrences of all spaces and special characters within a string in Swift.

I don't know what the RegEx would be in Swift.

I am trying to use the built in function .replacingOccurences(of:) and passing in my RegEx as the string-protocol, while the code compiles, no changes are made.

Online there are many resources on how to replace occurrences in Swift however, the solutions are far more complicated than what seems to be nessacary.

How can I properly return this output (Current Strategy):

let word = "Hello World!!"
func regEx(word: String) -> String {
   return word.replacingOccurrences(of: "/[^\\w]/g", with: "")
}
// return --> "HelloWorld"

Swift uses ICU regex library, I do not know any online regex tester that supports it, but PCRE is close though there is a considerable difference. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 16, 2018 at 20:06

Wiktor Stribiżew · Accepted Answer · 2018-07-16 20:14:58Z

5

You may use

return word.replacingOccurrences(of: "\\W+", with: "", options: .regularExpression)

Note the options: .regularExpression argument that actually enables regex-based search in the .replacingOccurrences method.

Your pattern is [^\w]. It is a negated character class that matches any char but a word char. So, it is equal to \W.

The /.../ are regex delimiters. In Swift regex, they are parsed as literal forward slashes, and thus your pattern did not work.

The g is a "global" modifier that let's a regex engine match multiple occurrences, but it only works where it is supported (e.g. in JavaScript). Since regex delimiters are not supported in Swift regex, the regex engine knows how to behave through the .replacingOccurrences method definition:

Returns a new string in which all occurrences of a target string in the receiver are replaced by another given string.

If you need to check ICU regex syntax, consider referring to ICU User Guide > Regular Expressions, it is the regex library used in Swift/Objective-C.

edited Jul 16, 2018 at 20:14

answered Jul 16, 2018 at 20:08

Wiktor Stribiżew

631k41 gold badges502 silver badges632 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Leo Dabus Over a year ago

You need to set the options to .regularExpression

Wiktor Stribiżew Over a year ago

Yeah, I was testing it now, and was going to update.

Chris Peragine · Accepted Answer · 2019-03-05 15:57:07Z

0

Additionally, you could extend String and accomplish the same bit. But if it's homework and they said function stick with that.

var word = "Hello World!!!"

extension String {
    func regEx() -> String {
        return self.replacingOccurrences(of: "\\W+", with: "", options: .regularExpression, range: nil)
    }
}

word.regEx()

answered Mar 5, 2019 at 15:57

Chris Peragine

1782 silver badges8 bronze badges

Collectives™ on Stack Overflow

Using regex in Swift

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related