Checking the right answer

This recipe will complete the previous one by checking the user's answer. If for any reason the answer receives a value out of range, this will be set to nil. Of course, in this application, it's not possible to answer with a wrong value, but remember that a good developer is always thinking about the possible software evolution.

Getting ready

Copy the previous recipe; if you like, you can rename the product name to Chapter 2 Examination 2 by simply renaming the target name, as shown here:

How to do it...

Follow these steps in order to check the answers:

1. Go to the question.swift file. Now, replace the current class with the following one:

   struct Question {
       var question:String
       var answer1:String
       var answer2:String
       var answer3:String
       var rightAnswer:Int
       var userAnswer:Int? {
           willSet(newAnswer){
               if newAnswer? < 2 || newAnswer? > 3 {
                   userAnswer = nil
                    println("Wrong value, fixing...