Swift utility class for regular expression

Regexp.swift

import Foundation

extension String {
    func isMatch(regexp:Regexp) -> Bool {
        let range = NSMakeRange(0, self.characters.count)
        let matches = regexp.internalRegexp.matchesInString(self, options: [], range:range )
        return matches.count > 0
    }
    
    func matches(regexp:Regexp) -> [String]? {
        guard self.isMatch(regexp) else { return nil }
        
        let range = NSMakeRange(0, self.characters.count)
        let matches = regexp.internalRegexp.matchesInString( self, options: [], range:range )
        
        return matches.map{ (self as NSString).substringWithRange($0.range) }
    }
    
    func replace(regexp:Regexp, replaceString: String) -> String? {
        let matchs = regexp.internalRegexp.stringByReplacingMatchesInString(self, options: [], range: NSMakeRange(0, self.characters.count), withTemplate: replaceString)
        return matchs
    }
}

class Regexp {
    let internalRegexp: NSRegularExpression
    let pattern: String
    
    init?(_ pattern: String) {
        self.pattern = pattern
        do {
            self.internalRegexp = try NSRegularExpression(pattern: pattern, options: .CaseInsensitive)
        } catch let error as NSError {
            print(error.localizedDescription)
            self.internalRegexp = NSRegularExpression()
            return nil
        }
    }
    
    func isMatch(input: String) -> Bool {
        return input.isMatch(self)
    }
    
    func matches(input: String) -> [String]? {
        return input.matches(self)
    }
    
    func replace(string: String, replaceString: String) -> String? {
        return string.replace(self, replaceString: replaceString)
    }
}

let pattern: String = "(http|https)://([a-zA-Z0-9]|.)+"
var string: String = "飼い主のブログは http://www.feelingplace.com/ です。"
var replaceString: String = "Feelingplace"

if let regexp = Regexp(pattern),
    let title = regexp.replace(string, replaceString: replaceString) {
        print(title) //飼い主のブログは Feelingplace です。
}

if let regexp = Regexp(pattern) {
    "飼い主のブログは http://www.feelingplace.com/ です。".isMatch(regexp)
    
    if let matches = "飼い主のブログは http://www.feelingplace.com/ です。".matches(regexp) {
        for match in matches {
            match
        }
    }
    
    "飼い主のブログは http://www.feelingplace.com/ です。".replace(regexp, replaceString: "Feelingplace")
}


func ~=(r: Regexp, s: String) -> Bool {
    return r.isMatch(s)
}

if
    let regexpAAA = Regexp("AAA"),
    let regexpBBB = Regexp("BBB"),
    let regexpCCC = Regexp("CCC")
{
    switch "AAX BBX CCC" {
    case regexpAAA:
        "AAA"
    case regexpBBB:
        "BBB"
    case regexpCCC:
        "CCC"
    default:
        ()
    }
}