performSegueWithIdentifier causes crash - swift

Question

I'm setting up a sign up/login page using framework PARSE on XCode 6.
When I try to perform a segue (it is spelled correcty), hover, the app crash, even though the segue is inside an if statement.
Here's the code:
import UIKit
import Parse
class ViewController: UIViewController, UINavigationControllerDelegate{
var signUpMode = false
func displayAlert(title:String, message:String){
let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
//Outlet and actions
#IBOutlet var username: customTextField!
#IBOutlet var email: customTextField!
#IBOutlet var password: customTextField!
//Need the outlets for changes betweeen signUp and logIn modes!!!
#IBAction func signUp(sender: AnyObject) {
if signUpMode == true {
var user = PFUser()
user.username = username.text
user.password = password.text
user.email = email.text
// other fields can be set just like with PFObject
//user["phone"] = "415-392-0202"
user.signUpInBackgroundWithBlock {
(succeeded: Bool!, error: NSError!) -> Void in
if error == nil {
// Hooray! Let them use the app now.
} else {
println("error")
self.displayAlert("Username already in use", message: "Please use another username")
}
}
}
else {
PFUser.logInWithUsernameInBackground(email.text, password:password.text) {
(user: PFUser!, error: NSError!) -> Void in
if user != nil {
self.displayAlert("You're in", message: "And you'll be successful")
self.performSegueWithIdentifier("goToPost", sender: self)
} else {
self.displayAlert("Wrong username or password", message: "Please try again")
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewWillAppear(animated: Bool) {
if signUpMode == false {
self.username.hidden = true
self.email.placeholder = "username"
}
}
override func viewDidAppear(animated: Bool) {
if PFUser.currentUser() != nil {
performSegueWithIdentifier("goToPost", sender: self)
}
}
}
The segue is inside the viewWillAppear method.
PFUser().currentUser() stores information about the current logged in user, so it's nil if no user is logged in.
Can you find out why it crashes?
I tried to put the segue inside viewDidLoad, but nothing else, it didn't even crashed.

Answer 1

Try segueing in viewDidAppear: and check if your segue identifier matches the one on your storyboard.