如何在 Swift 中以编程方式阻止 segue？

Question

Here is the code:

    @IBAction func loginTapped(_ sender: Any) {

    let email = emailTextField.text!.trimmingCharacters(in: .whitespacesAndNewlines)
    let password = passwordTextField.text!.trimmingCharacters(in: .whitespacesAndNewlines)

    Auth.auth().signIn(withEmail: email, password: password) { (result, error) in

        if error != nil {
            self.errorLabel.text = error!.localizedDescription
            self.errorLabel.alpha = 1
            print(error!.localizedDescription)
        }
        else {

            self.performSegue(withIdentifier: "loginSegue", sender: nil)

            print("User is signed in with Firebase.")
        }
    }
}

I have a segue, loginSegue , connected from the login button to the homeViewController . Within in the if error statement I would like to stop the segue from going through because the user has not signed in. The goal here is not allow the user to go forward if they get an error. Is there an "opposite" to the performSegue(withIdentifier: String, sender: Any?) ?

Answer 1

I think your button is connected to perform segue in storyboard. So your button has two actions - one from storyboard to perform segue and second in your code. Just remove the connection from storyboard and connect only UIViewControllers not with your button.

Answer 2

First, there is no opposite of performSegue(withIdentifier: String, sender: Any?)?

But issue is not about it. I think u you connected segue with login button and gave it a identify. If you give a button a segue directly, button always gonna show which page you connected with. Doing some operations in button action doesnt effect.

You need to add this segue to FirstVc to SecondVc ( not to button) and then give identify this segue then control when login button tapped. If no error run segue with giving identify and show it.

Answer 3

You could override the shouldPerformSegue(withIdentifier:,sender:) method and return false if the login fails and you don't want to perform the segue. Here's an example

override func shouldPerformSegue(withIdentifier identifier: String?, sender: Any?) -> Bool {
    if let ident = identifier {
        if ident == "YourIdentifier" {
            if loginSuccess != true {
                return false
            }
        }
    }
    return true
}