Swift extension to NSMutableAttributedString adding methods for highlighting and replacing substrings (swift 2.0 supportted)

Swift extension to NSMutableAttributedString (highlight and replace)

extension NSMutableAttributedString {
    
    func highlightStrings(stringToHighlight:String, usingRegex:Bool = false) {
        
        var useRegex:NSRegularExpressionOptions?
        
        
        if !usingRegex {
            useRegex = NSRegularExpressionOptions.IgnoreMetacharacters
        }
        let exp = try! NSRegularExpression(pattern: stringToHighlight, options: useRegex!)
        
        let arr = exp.matchesInString(self.string, options: [], range:NSRange(location: 0, length: self.length))
        
        for s in arr {
            
            self.addAttribute(NSBackgroundColorAttributeName, value: UIColor.greenColor(), range: s.range)
            
        }
        
    }
    
    func replaceStrings(find:String, replace:String, usingRegex:Bool = false) {
        
//        var useRegex:NSRegularExpressionOptions?
//        if !usingRegex {
//            useRegex = NSRegularExpressionOptions.IgnoreMetacharacters
//        }
//        
//        let exp = try! NSRegularExpression(pattern: find, options: useRegex!)
//        let arr = exp.matchesInString(self.string, options: [], range:NSRange(location: 0, length: self.length))
        
        self.mutableString.replaceOccurrencesOfString(find, withString:replace, options:NSStringCompareOptions.RegularExpressionSearch, range:NSRange(location: 0, length: self.length))
        
    }
}