Grabbing correct PFErrorCode for an error returned in a Parse cloud code response

PFErrorHelper.swift

// Class that can retrieve nested error messages from Parse cloud code responses
//
// If you've got cloud code that does something like
//
//    thing.save().then(function(savedThing) {
//        response.success();
//    }, function(error) {
//        response.error(error);
//    });
// 
// Then you might have had issues trying to get the real error code from a returned error response.
// That's because when you call `response.error(error)`, you're not responding with the error object
// itself, you're translating it into a string and adding it as an optional message on the error response.
//
// This means that all of the errors returned by your cloud code will all have code 141 when you inspect them,
// and the true error code/message are hidden in the error's `userInfo` dictionary as a String.
// To get the real error code, you'll need to dig in to find the stringified error, convert it to JSON, and
// construct your own error code off of that.

class PFErrorHelper {
    class func nestedErrorCode(error: NSError) -> PFErrorCode {
        if let innerDict = error.userInfo, errorMessageString = innerDict["error"] as? NSString, jsonData = errorMessageString.dataUsingEncoding(NSUTF8StringEncoding) {
            var parsingError: NSError?
            if let json = NSJSONSerialization.JSONObjectWithData(jsonData, options: NSJSONReadingOptions.AllowFragments, error: &parsingError) as? [NSString : AnyObject], code = json["code"] as? Int, errorCode = PFErrorCode(rawValue: code) {
                return errorCode
            } else if parsingError != nil {
                NSLog("Error determining nested error: \(parsingError)")
                return PFErrorCode.ErrorInternalServer
            }
        }
        return PFErrorCode.ErrorInternalServer
    }
}