Regex.swift

import Foundation

enum SteakerRegex {
    case email
    case password
    case address(String)
    case chineseCharacter

    var rawRegex: String {
        switch self {
        case .email:
            return #"^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$"#
        case .password:
            return #"(?=.*\d)(?=.*[A-Za-z]).{8,}"#
        case .address(let addressRegex):
            return addressRegex
        case .chineseCharacter:
            // https://stackoverflow.com/questions/11897531/detecting-if-nsstring-contains-chinese-characters/11898220#11898220
            return #"\p{script=Han}"#
        }
    }
}

extension String {

    func validate(regex: SteakerRegex) -> Bool {
        !match(regex: regex.rawRegex).isEmpty
    }

    func match(regex pattern: String) -> [String] {
        do {
            let text = self
            let regex = try NSRegularExpression(pattern: pattern)
            let matches = regex.matches(in: text,
                                        range: NSRange(text.startIndex..., in: text))
            return matches.flatMap { match in
                (0..<match.numberOfRanges).map {
                    let rangeBounds = match.range(at: $0)
                    guard let range = Range(rangeBounds, in: text) else {
                        return ""
                    }
                    return String(text[range])
                }
            }
        } catch {
            return []
        }
    }

    /// To check if this string is contains only chinese characters.
    /// Empty string will return false.
    func checkIfPureChineseString() -> Bool {
        guard !isEmpty else { return false }

        let originCharacterCount = self.count
        let chineseCharacterCount = self.match(regex: SteakerRegex.chineseCharacter.rawRegex).count
        return originCharacterCount == chineseCharacterCount
    }
}