JSONSerialization makes incorrect JSON object. Swift - node.js

Question

I'm creating an iOS app that connects to a NodeJS server. The get method works fine but the POST method has problems.
var urlRequest = URLRequest(url: "http://localhost:3000/register")
urlRequest.httpMethod = "POST"
let info: [String:Any] = ["username": "username", "password":"username", "email":"username#username.com"]
do {
let jsonInfo = try
JSONSerialization.data(withJSONObject: info, options[])
urlRequest.httpBody = jsonInfo
} catch {
print("ERROR")
return
}
The request gets sent but something goes wrong with JSONSerialization because this is the JSON data that the server gets:
{'{"email":"username#username.com","username":"username","password":"username"}': '' }
This is what I'm going for:
{"email":"username#username.com","username":"username","password":"username"}
This is part of the server code:
const express = require('express');
const bodyParser = require('body-parser');
var app = express();
var allowMethods = function(req, res, next) {
res.header('Access-Control-Allow-Methods', 'GET, POST, PATCH, PUT, DELETE');
next();
}
http.createServer(app).listen(3001);
console.log("Server started");
app.use(bodyParser.urlencoded({extended: true}));
app.use(allowMethods);
const _ = require('lodash');
let b = _.pick(req.body, ['username', 'password', 'email']);
Any ideas on what I'm doing wrong? I'd like to avoid using alamofire if possible. I've tried changing the format of the dictionary but always turns out as:
{ 'the whole dictionary is the key': ''}
I've also tried using pretty print and this was the result:
{ '{\n "email" : "username#username.com",\n "username" : "username",\n "password" : "username"\n}': '' }
Any help is appreciated. Thank you!
EDIT:
I tried Mike Taverne's suggestions.
I changed the server code to use this instead:
app.use(bodyParser.json());
But I receive an empty body from the simulator.
I also added these to the swift code:
urlRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
urlRequest.addValue("application/json", forHTTPHeaderField: "Accept")
But the server also receives an empty body and by empty body I mean the data I'm trying to send is received as empty by the server. When I check the httpBody the data is there but for some reason the server doesn't receive it.

Answer 1

I believe your Swift code is fine. When I did this in a playground:
print(String(data: urlRequest.httpBody!, encoding: String.Encoding.utf8)!)
It printed:
{"username":"username","password":"username","email":"username#username.com"}
I'm not an expert on body-parser, but I think that instead of this:
bodyParser.urlencoded({extended: true})
You should be using this:
bodyParser.json([options]) //not sure which options exactly you need
You may need to set Content-Type: application/json header as well. Refer to the body-parser documentation for more info.

Answer 2

I solved it by changing the data itself. Instead of forcing it to pass JSON I passed it as a string encoded using UTF8
let dataString = "username=username&password=username&email=username#username.com"
urlRequest.httpBody = dataString.data(using: .utf8)
I got the answer by using the method in this post:
HTTP Request in Swift with POST method