Sending string from Node.js (Express) server to iOS Swift 3 - ios

Question

I am trying to create a login system for my iOS mobile application. I have a request sending to my Node.js server with Swift 3 with:
#IBAction func loginBtn(_ sender: UIButton) {
//created NSURL
let requestURL = NSURL(string: loginURL)
//creating NSMutableURLRequest
let request = NSMutableURLRequest(url: requestURL! as URL)
//setting the method to post
request.httpMethod = "POST"
//getting values from text fields
let empNum = empTextField.text
let empPass = passTextField.text
//creating the post parameter by concatenating the keys and values from text field
let postParameters = "empNum=" + empNum! + "&empPass=" + empPass!;
//adding the parameters to request body
request.httpBody = postParameters.data(using: String.Encoding.utf8)
//creating a task to send the post request
let task = URLSession.shared.dataTask(with: request as URLRequest){
data, response, error in
if error != nil{
print("error is \(String(describing: error))")
return;
}
//parsing the response
do {
//converting resonse to NSDictionary
let myJSON = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
print("myjson : \(String(describing: myJSON))")
//parsing the json
if let parseJSON = myJSON {
//creating a string
var msg : String!
//getting the json response
msg = parseJSON["message"] as! String?
//printing the response
print("message here: \(msg)")
}
} catch {
print("Error here: \(error)")
}
}
//executing the task
task.resume()
}
I am getting a 200 server side but I want to be able to res.send a string back to Swift so I can proceed to take further actions. How do I check that response? Like:
if response == "vaild" {
...
}else{
...
}
When I run this code I get an error that reads:
Error here: Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}
P.S. I am also not really familiar with the request code so if it is right in front of my face please just explain the code to me then. Sorry in advance!!

Answer 1

Your code sample suggests that your client expects a json response with a property message in it. If you are using resp.send('Success') from your server it will not be a json object. It will be a string.
If that is what you want on your server response you should update your client to simply parse the data to a string. You can use String(data: data, encoding: .utf8) where "data" is what is returned from the response.
However, I would recommend leveraging HTTP Status codes. In your server code you can respond with a 422 if login was not successful. This can be accomplished with resp.status(422).send('Some optional message'). Then client side all you need to do is check the response status. Instead of a string compare.