MacOS complete post request then segue

Question

I am developing a MacOS app that has a login page. When the user pressed the login button i need to send a post request and if the response is code is 200 then i need to preform a segue.

I am running into an issue where the segue is occurring no matter what i try

I have tried using the IBAction for a button then calling preform segue however that resulted in a thread problem. I have now put everything in shouldPerformSegue

override func shouldPerformSegue(withIdentifier identifier: NSStoryboardSegue.Identifier, sender: Any?) -> Bool {

        if emailTextField.stringValue.isEmpty || passwordTextField.stringValue.isEmpty {
            instructionText.stringValue = "Email and Password Required"
            return false
        }

        let emailPassword = "email="+emailTextField.stringValue+"&password="+passwordTextField.stringValue
        print("before post")
        let data = emailPassword.data(using: String.Encoding.ascii, allowLossyConversion: false)
        let url = URL(string: "http://127.0.0.1:50896/api/v1/auth")!
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.httpBody = data
        let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
            if let error = error {
                print("error: \(error)")
            } else {
                if let response = response as? HTTPURLResponse {
                    print("statusCode: \(response.statusCode)")
                }
                if let data = data, let dataString = String(data: data, encoding: .utf8) {
                    print("data: \(dataString)")
                }
            }
        }
        task.resume()

        return true
    }

I would like to complete the post request, check response code then preform segue if the code is 200

It’s impossible to return something depending on the result of an asynchronous task in `shouldPerformSegue`. — vadian, Apr 23 '19 at 15:01

score 0 · Accepted Answer · answered Apr 23 '19 at 15:00

The problem is - The task.resume() is asynchronous; its result is therefore useless, because you are already returning from shouldPerformSegue() with a true value. What that essentially means is that the task is executed sometime AFTER you said "It's ok to perform a segue". Instead, call the task from the buttons IBAction, and perform segue in 200 status code section. Good luck!

Edit: The thread problem with the IBAction is probably because you are doing main-thread stuff on an off-thread (UI updates, performSegue, ...). Check out In Swift how to call method with parameters on GCD main thread?

score 0 · Answer 2 · answered Apr 23 '19 at 16:33

One way of doing it is using with completion callback using closures.

func shouldPerformSegue(withIdentifier identifier: NSStoryboardSegue.Identifier, sender: Any?,OnSucess sucess:@escaping(Bool)->Void){
    let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
        if let error = error {
            print("error: \(error)")
            sucess(false)
        } else
        {
            if let response = response as? HTTPURLResponse {

                print("statusCode: \(response.statusCode)")
            }
            if let data = data, let dataString = String(data: data, encoding: .utf8) {
                print("data: \(dataString)")
            }
            sucess(true)
        }
    }
}

let identiferStory: NSStoryboardSegue.Identifier = "main"
shouldPerformSegue(withIdentifier: identiferStory, sender: nil) { (isSucess) in
    if isSucess == true{

    }
    else{

    }
}

`shouldPerformSegue` is a method of `UIViewController`. If you change the signature it’s never going to be called. — vadian, Apr 23 '19 at 16:41
Thank you for point that out @vadian. I was unaware of that. In that case maybe you can write another completion callback using closures and call it from shouldPerformSegue function. — kathmandu, Apr 23 '19 at 17:16

MacOS complete post request then segue

2 Answers2