how to perform Condition check, before segue unwind

Question

VC1 segues to VC3 which has a keypad and predetermined lowest number acceptable entered into a label. User can either add a number to the end of th

Answer 1

To achieve this, connect Controller of VC3 to its own exit and select the unwind action.

Give this exit-segue a segue.identifier "YOUR EXIT TEXT"

Still in VC3, create an IBAction for the "Accept" button.

@IBAction func accept(sender: AnyObject) {
    if //Condition X is true
        {performSegueWithIdentifier("YOUR EXIT TEXT", sender: self)}
    else {
        //Do this
        }