Stop Segue and pass to next view the content of textfield shown in alert - Swift

I need to stop a segue transition and show alert with a textField. But then, when I press "OK" button, I want to pass to the next view, the content of the textfield.

The problem is when I declare a view controller destination in prepareForSegue and I pass the text, because this is nil. I write my expample:

override func shouldPerformSegueWithIdentifier(identifier: String?, sender: AnyObject?) -> Bool {
    var shouldSegue:Bool = true
    if identifier == "FirstToSecondView" {

        var alert = UIAlertController(title: "End the First", message: "Are you sure you want to end the first?", preferredStyle: UIAlertControllerStyle.Alert)
        alert.addTextFieldWithConfigurationHandler{ (textField) in
               textField.placeHolder = "Name"
        }
        presentViewController(alert, animated: true, completion: nil)

        var okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) {
            UIAlertAction in
            println("OK Pressed")
            let tf = alert.textFields?.First as? UITextField

            //name is a declared variable above
            if tf != nil {self.name = tf.text}

            self.performSegueWithIdentifier("WorkoutToSummary", sender: self)
        }
        var cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) {
            UIAlertAction in
            println("Cancel Pressed")
            shouldSegue = false
        }
        alert.addAction(okAction)
        alert.addAction(cancelAction)
    }
    return shouldSegue
}

And then in the prepareForSegue, I put that:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?){
    var namePass: String = self.name
    if segue.identifier == "FirstToSecondView" {
        let secondViewController = segue.destinationViewController as SecondViewController
        secondViewController.name = namePass
    }
}

But at the moment that prepareForSegue is launched, self.name is nil

Thanks in advance!!