Swift 'Required String parameter 'grant_type' is not present' error when trying to get an access token - swift

Question

So I'm trying to make an app in Swift for which I need to login to the OAuth to retrieve an access token. The API takes the parameters 'grant_type' and 'code'.
I've tried:
let params = ["grant_type":"authorization_code", "code":"123456789"] as Dictionary<String, String>
var request = URLRequest(url: URL(string: "https://myschool.zportal.nl/api/v3/oauth/token")!)
request.httpMethod = "POST"
request.httpBody = try? JSONSerialization.data(withJSONObject: params, options: [])
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
let session = URLSession.shared
let task = session.dataTask(with: request, completionHandler: { data, response, error -> Void in
do {
let json = try JSONSerialization.jsonObject(with: data!) as! Dictionary<String, AnyObject>
print(json)
} catch {
print("error")
}
})
task.resume()
This returns:
["response": {
data = (
);
details = "class org.springframework.web.bind.MissingServletRequestParameterException: Required String parameter 'grant_type' is not present";
endRow = 0;
eventId = 216795;
message = "Internal problems.";
startRow = 0;
status = 500;
totalRows = 0;
}]
This is weird, because I did parse the 'grant_type' parameter, and as the correct value.
It should return something like:
{
"response": {
"status":200,
"message":"",
"startRow":0,
"endRow":27,
"totalRows":27,
"data":[
{
},
...
]
}
}

Answer 1

The standard message format requires a Form URL Encoded body, not a JSON one. Maybe adapt your code as in this Swift article.

Answer 2

Got it working:
#IBAction func sendButtonPressed(_ sender: UIButton) {
let urlString = "https://myschool.zportal.nl/api/v3/oauth/token"
performRequest(urlString: urlString)
}
func performRequest(urlString: String) {
if let url = URL(string: urlString) {
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.httpBody = "grant_type=authorization_code&code=1234567890".data(using: .utf8)
let session = URLSession(configuration: .default)
let task = session.dataTask(with: request, completionHandler: { data, response, error -> Void in
//print(response!)
do {
let json = try JSONSerialization.jsonObject(with: data!) as! Dictionary<String, AnyObject>
print(json)
} catch {
print("error")
}
})
task.resume()
}
}
Not the nicest code but I'll polish it later.
At first I parsed JSON but it turned out I needed to parse a String and turn it into a Data type using: .data(using: .utf8)