Swift Regular Expression Checks Using Pattern Matching Examples

examples.swift

// *** different ways a string can match using our pattern matching operator ***
enum StringMatchType {
    case literal
    case escapedRegularExpression
    case regularExpression(withOptions: NSRegularExpression.Options)
}

/* *** example function that returns how the string matches against
a literal string and a regex pattern in default and case insensitive modes *** */
func typeOfMatch(for string: String) -> StringMatchType? {
    switch string {
    case "regex is fun!": 
        return .literal
    case "/.*is fun!/": 
        return .escapedRegularExpression
    case RegexPattern(".*is fun!", options: .caseInsensitive): 
        return .regularExpression(withOptions: .caseInsensitive)
    default: 
        return .none
    }
}

// *** testing the switch statement ***
typeOfMatch(for: "regex is fun!") // matches literal "regex is fun!"
typeOfMatch(for: "swift is fun!") // matches escaped regex ".*is fun!"
typeOfMatch(for: "swift IS fun!") // matches case insensitive regex ".*is fun!"
typeOfMatch(for: "swift is really fun!") // no match, breaks the ".*is fun!" pattern