Swift Language NSRegularExpression in Swift Extending String to do simple pattern matching
Example
extension String {
func matchesPattern(pattern: String) -> Bool {
do {
let regex = try NSRegularExpression(pattern: pattern,
options: NSRegularExpressionOptions(rawValue: 0))
let range: NSRange = NSMakeRange(0, self.characters.count)
let matches = regex.matchesInString(self, options: NSMatchingOptions(), range: range)
return matches.count > 0
} catch _ {
return false
}
}
}
// very basic examples - check for specific strings
dump("Pinkman".matchesPattern("(White|Pinkman|Goodman|Schrader|Fring)"))
// using character groups to check for similar-sounding impressionist painters
dump("Monet".matchesPattern("(M[oa]net)"))
dump("Manet".matchesPattern("(M[oa]net)"))
dump("Money".matchesPattern("(M[oa]net)")) // false
// check surname is in list
dump("Skyler White".matchesPattern("\\w+ (White|Pinkman|Goodman|Schrader|Fring)"))
// check if string looks like a UK stock ticker
dump("VOD.L".matchesPattern("[A-Z]{2,3}\\.L"))
dump("BP.L".matchesPattern("[A-Z]{2,3}\\.L"))
// check entire string is printable ASCII characters
dump("tab\tformatted text".matchesPattern("^[\u{0020}-\u{007e}]*$"))
// Unicode example: check if string contains a playing card suit
dump("♠︎".matchesPattern("[\u{2660}-\u{2667}]"))
dump("♡".matchesPattern("[\u{2660}-\u{2667}]"))
dump("😂".matchesPattern("[\u{2660}-\u{2667}]")) // false
// NOTE: regex needs Unicode-escaped characters
dump("♣︎".matchesPattern("♣︎")) // does NOT work
Below is another example which builds on the above to do something useful, which can't easily be done by any other method and lends itself well to a regex solution.
// Pattern validation for a UK postcode.
// This simply checks that the format looks like a valid UK postcode and should not fail on false positives.
private func isPostcodeValid(postcode: String) -> Bool {
return postcode.matchesPattern("^[A-Z]{1,2}([0-9][A-Z]|[0-9]{1,2})\\s[0-9][A-Z]{2}")
}
// valid patterns (from https://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdom#Validation)
// will return true
dump(isPostcodeValid("EC1A 1BB"))
dump(isPostcodeValid("W1A 0AX"))
dump(isPostcodeValid("M1 1AE"))
dump(isPostcodeValid("B33 8TH"))
dump(isPostcodeValid("CR2 6XH"))
dump(isPostcodeValid("DN55 1PT"))
// some invalid patterns
// will return false
dump(isPostcodeValid("EC12A 1BB"))
dump(isPostcodeValid("CRB1 6XH"))
dump(isPostcodeValid("CR 6XH"))
