JSONSerialization Invalid type in JSON write (_SwiftValue)

Question

Why does the following code give me the error:

Invalid type in JSON write (_SwiftValue).

The error is thrown on this line:

Answer 1

If you're using SwiftyJSON to access a JSON object, it's important to use the dictionaryObject property of the JSON (instead of using dictionaryValue, dictionary or nothing at all), because you will get this error (or a variation of it) otherwise. For example:

guard let jsonDict = json.dictionaryObject else {
    return
}

let jsonData = try JSONSerialization.data(withJSONObject: jsonDict, options: [])