Filter non-digits from string

Question

Using only swift code I cant figure out how to take \"(555) 555-5555\" and return only the numeric values and get \"5555555555\". I need to remove all the parentheses, whit

Answer 1

Details

• Xcode Version 10.2.1 (10E1001), Swift 5

Solution

import Foundation

extension String {

    private func filterCharacters(unicodeScalarsFilter closure: (UnicodeScalar) -> Bool) -> String {
        return String(String.UnicodeScalarView(unicodeScalars.filter { closure($0) }))
    }

    private func filterCharacters(definedIn charSets: [CharacterSet], unicodeScalarsFilter: (CharacterSet, UnicodeScalar) -> Bool) -> String {
        if charSets.isEmpty { return self }
        let charSet = charSets.reduce(CharacterSet()) { return $0.union($1) }
        return filterCharacters { unicodeScalarsFilter(charSet, $0) }
    }

    func removeCharacters(charSets: [CharacterSet]) -> String { return filterCharacters(definedIn: charSets) { !$0.contains($1) } }
    func removeCharacters(charSet: CharacterSet) -> String { return removeCharacters(charSets: [charSet]) }

    func onlyCharacters(charSets: [CharacterSet]) -> String { return filterCharacters(definedIn: charSets) { $0.contains($1) } }
    func onlyCharacters(charSet: CharacterSet) -> String { return onlyCharacters(charSets: [charSet]) }
}

Usage

let string = "23f45gdor#@%#i425v wer 24 1+DWEJwi 3u09ru49w*()9uE2R_)$I#Q)_ U383q04+RFJO{dgnkvlj b`kefl;nwdl qsa`WKFSA,.E"
print("original string:                                 \(string)")
print("only .decimalDigits:                             \(string.onlyCharacters(charSet: .decimalDigits))")
print("only [.lowercaseLetters, .symbols]:              \(string.onlyCharacters(charSets: [.lowercaseLetters, .symbols]))")
print("remove .letters:                                 \(string.removeCharacters(charSet: .letters))")
print("remove [.decimalDigits, .lowercaseLetters]:      \(string.removeCharacters(charSets: [.decimalDigits, .lowercaseLetters]))")

Result

original string:                                 23f45gdor#@%#i425v wer 24 1+DWEJwi 3u09ru49w*()9uE2R_)$I#Q)_ U383q04+RFJO{dgnkvlj b`kefl;nwdl qsa`WKFSA,.E
only .decimalDigits:                             2345425241309499238304
only [.lowercaseLetters, .symbols]:              fgdorivwer+wiuruwu$q+dgnkvljb`keflnwdlqsa`
remove .letters:                                 2345#@%#425  24 1+ 30949*()92_)$#)_ 38304+{ `; `,.
remove [.decimalDigits, .lowercaseLetters]:      #@%#   +DWEJ *()ER_)$I#Q)_ U+RFJO{ `; `WKFSA,.E

---

(Optional) String extension

extension String {
    var onlyDigits: String { return onlyCharacters(charSets: [.decimalDigits]) }
    var onlyLetters: String { return onlyCharacters(charSets: [.letters]) }
}

(Optional) String extension usage

let string = "23f45gdor#@%#i425v wer 24 1+DWEJwi 3u09ru49w*()9uE2R_)$I#Q)_ U383q04+RFJO{dgnkvlj b`kefl;nwdl qsa`WKFSA,.E"
print("original string:     \(string)")
print(".onlyDigits:         \(string.onlyDigits)")
print(".onlyLetters:        \(string.onlyLetters)")

(Optional) String extension usage result

original string:     23f45gdor#@%#i425v wer 24 1+DWEJwi 3u09ru49w*()9uE2R_)$I#Q)_ U383q04+RFJO{dgnkvlj b`kefl;nwdl qsa`WKFSA,.E
.onlyDigits:         2345425241309499238304
.onlyLetters:        fgdorivwerDWEJwiuruwuERIQUqRFJOdgnkvljbkeflnwdlqsaWKFSAE