Swift: checking if a String is valid JSON

I’ve been developing an application that produces a JSON string for use online. Pretty simple, but I want to make sure the JSON is valid (since a user can edit the JSON by hand if they want to before using the JSON string). How can you quickly validate your JSON?

let jsonString = composedString
if let jsonDataToVerify = jsonString.data(using: String.Encoding.utf8)
{
    do {
        _ = try JSONSerialization.jsonObject(with: jsonDataToVerify)
        print("JSON is valid.")
    } catch {
        print("Error deserializing JSON: \(error.localizedDescription)")
    }
}

Pretty easy.