Convert String to base64 String

StringBase64.swift

extension String {
    
    var base64 : String?
    {
        if let convertedData = self.dataUsingEncoding(NSUTF8StringEncoding)
        {
            let convertedDataBase64 = convertedData.base64EncodedDataWithOptions(NSDataBase64EncodingOptions(rawValue: 0))
            let stringBase64 = String(data: convertedDataBase64, encoding: NSUTF8StringEncoding)
            
            return stringBase64
        }
        return nil
    }
    
}