A generic signup / login form for an iOS app written in Swift. NOTE: This uses Parse for user management. Put your Parse credentials in your AppDelegate.swift file.

loginsignup.swift

import UIKit

class ViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
    
    var signupActive = true
    
    var activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView()
    
    func displayAlert(title: String, error:String){
        var alert = UIAlertController(title: title, message: error, preferredStyle: UIAlertControllerStyle.Alert)
        
        alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { action in
            
            self.dismissViewControllerAnimated(true, completion: nil)
            
        }))
        
        self.presentViewController(alert, animated: true, completion: nil)

    }

    @IBOutlet weak var username: UITextField!
    @IBOutlet weak var password: UITextField!
    
    @IBOutlet weak var alreadyRegistered: UILabel!
    @IBOutlet weak var signUpLabel: UILabel!
    
    @IBOutlet weak var signUpButton: UIButton!
    
    @IBAction func toggleSignUp(sender: AnyObject) {
        
        if signupActive == true {
            
            signupActive = false
            signUpLabel.text = "Use the form below to log in"
            signUpButton.setTitle("Log In", forState: UIControlState.Normal)
            alreadyRegistered.text = "Not registered?"
            signUpToggleButton.setTitle("Sign Up", forState: UIControlState.Normal)
            
        } else {
            
            signupActive = true
            signUpLabel.text = "Use the form below to sign up"
            signUpButton.setTitle("Sign Up", forState: UIControlState.Normal)
            alreadyRegistered.text = "Already registered?"
            signUpToggleButton.setTitle("Log In", forState: UIControlState.Normal)
            
        }
        
    }
    @IBOutlet weak var signUpToggleButton: UIButton!
    
    @IBAction func signUp(sender: AnyObject) {
        
        var error = ""
        
        if username.text == "" || password.text == "" {
            error = "Please enter a username and password."
        }
        if countElements(username.text) < 6 {
            error = "Username must be at least six characters"
        }
        if countElements(password.text) < 6 {
            error = "Password must be at least six characters."
        }
        
        if error != "" {
            
            displayAlert("Error in form.", error: error)
            
        } else {
            
            activityIndicator = UIActivityIndicatorView(frame: CGRectMake(0, 0, 50, 50))
            activityIndicator.center = self.view.center
            activityIndicator.hidesWhenStopped = true
            activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.Gray
            view.addSubview(activityIndicator)
            activityIndicator.startAnimating()
            UIApplication.sharedApplication().beginIgnoringInteractionEvents()
            
            if signupActive == true {
                
                var user = PFUser()
                user.username = username.text
                user.password = password.text
                //user.email = "email@example.com"
                // other fields can be set just like with PFObject
            
                user.signUpInBackgroundWithBlock {
                    (succeeded: Bool!, signupError: NSError!) -> Void in
                
                    self.activityIndicator.stopAnimating()
                    UIApplication.sharedApplication().endIgnoringInteractionEvents()
                
                    if signupError == nil {
                        println("signed up")
                        // Hooray! Let them use the app now.
                    } else {
                    
                        if let errorString = signupError.userInfo?["error"] as? NSString{
                            error = errorString
                        } else {
                            error = "Please try again later."
                        }
                    
                    
                        self.displayAlert("Could Not Sign Up", error: error)

                    }
                }
            } else {
                PFUser.logInWithUsernameInBackground(username.text, password: password.text) {
                    (user: PFUser!, signupError: NSError!) -> Void in
                    
                    self.activityIndicator.stopAnimating()
                    UIApplication.sharedApplication().endIgnoringInteractionEvents()

                    if signupError == nil {
                        // Do stuff after successful login.
                        println("logged in")
                    } else {
                            
                        if let errorString = signupError.userInfo?["error"] as? NSString{
                            error = errorString
                        } else {
                            error = "Please try again later."
                        }
                    
                        self.displayAlert("Could Not Log In", error: error)

                    }
                }
            }
        }
    }

    
    override func viewDidLoad() {
        super.viewDidLoad()


    } // end viewDidLoad

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}