Using two values from a function

Question

I've started to make a basic quiz game using Swift. I've written a struct to define what I want relating to each question:

struct Question {
  let question: String
  let answers: [String]
  let correctAnswer: Int
}

The game will be a basic maths quiz, so will show random maths questions. I've written a function to randomise the questions and obtain the answers:

func questionAnswerBuilder() -> (question: String, answer: String) {
let first: Int = randomNumber()
let second: Int = randomNumber()
let arr = [first,second].sorted(by: >)

let firstAsString = String(arr[0])
let secondAsString = String(arr[1])

let questionString = "\(firstAsString) + \(secondAsString)"
let question = questionString

//Answer:
let answerString = first + second
let answer = String(answerString)

return (question, answer)
}

I have tested this in playgrounds and it works fine. Each time it creates a random number and outputs that along with the correct answer. Now I'd like to use this in each question...

var questionTest = questionAnswerBuilder()

var questions: [Question] = [
Question(question: questionTest.question, answers: [randomAnswer(), randomAnswer(), questionAnswerBuilder().answer, randomAnswer()], correctAnswer: 2),
Question(question: questionTest.question, answers: [randomAnswer(), randomAnswer(), questionAnswerBuilder().answer, randomAnswer()], correctAnswer: 2)
]

For info, the randomAnswer() function is not displayed here. It's basically just a random number generator.

When I input all of this into Xcode I get the following message: Cannot use instance member 'questionTest' within property initializer; property initializers run before 'self' is available.

I currently have the questionAnswerBuilder() function in its own swift file. I have tried moving this to the same file as my questions variable but I still get the same fault. I have also tried making the questionTest variable lazy but this makes no difference.

Please please please could someone point out where I am going wrong!

Thanks in advance!

score 0 · Answer 1 · answered Nov 24 '18 at 16:29

0

Oh, you can’t use instance variables inside other instance variables.

You could fix this by changing your questions array to lazy var questions.

This will not create the array at the point of instantiating it. It will only create the array the first time you access it.

answered Nov 24 '18 at 16:29

Fogmeister

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Thanks for your answer. I had already seen the post you have marked as a duplicate - it makes more sense now! Thanks – evorg88 Nov 24 '18 at 16:47

score 0 · Accepted Answer · answered Nov 24 '18 at 16:29

You cannot initialize properties which depend on each other on the top level of a class.

A solution is to initialize questions lazily

lazy var questions: [Question] = {
    return [Question(question: questionTest.question, answers: [randomAnswer(), randomAnswer(), questionAnswerBuilder().answer, randomAnswer()], correctAnswer: 2),
            Question(question: questionTest.question, answers: [randomAnswer(), randomAnswer(), questionAnswerBuilder().answer, randomAnswer()], correctAnswer: 2)]
}()

Excellent it worked! Thank you very much for your help! – evorg88 Nov 24 '18 at 16:46 — evorg88, Nov 24 '18 at 16:46

Using two values from a function

2 Answers2