Using arc4random to generate ten random numbers - ios

Question

I am using arc4random to generate 10 random numbers so I can then query firebase to get the questions that contain the randomly generated numbers. The problem is that I don't want any number to appear more than once so then there are not duplicate questions. Current code below...
import UIKit
import Firebase
class QuestionViewController: UIViewController {
var amountOfQuestions: UInt32 = 40
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
// Use a for loop to get 10 questions
for _ in 1...10{
// generate a random number between 1 and the amount of questions you have
let randomNumber = Int(arc4random_uniform(amountOfQuestions - 1)) + 1
print(randomNumber)
// The reference to your questions in firebase (this is an example from firebase itself)
let ref = Firebase(url: "https://test.firebaseio.com/questions")
// Order the questions on their value and get the one that has the random value
ref.queryOrderedByChild("value").queryEqualToValue(randomNumber)
.observeEventType(.ChildAdded, withBlock: {
snapshot in
// Do something with the question
print(snapshot.key)
})
}
}
#IBAction func truepressed(sender: AnyObject) {
}
#IBAction func falsePressed(sender: AnyObject) {
}
}

Answer 1

You can have an array to store the value you want to random with, in your case, [1,2,3....10], and then use arc4random to get the random index of any value inside (0..9), get the value and remove it from array. Then you will never get the same number from the array.

Answer 2

Given the total number of questions
let questionsCount = 100
you can generate a sequence of integers
var naturals = [Int](0..<questionsCount)
Now given the quantity of unique random numbers you need
let randomsCount = 10
that of course should not exceed the total number of questions
assert(randomsCount <= questionsCount)
you can build your list of unique integers
let uniqueRandoms = (1..<randomsCount).map { _ -> Int in
let index = Int(arc4random_uniform(UInt32(naturals.count)))
return naturals.removeAtIndex(index)
}

Answer 3

As an alternative to generating the random number on the client and requesting a question at that specified number, you could download the entire array of questions and shuffle the array. GameKit provides a built-in method to shuffle the array.
import GameKit
// ...
let ref = Firebase(url: "https://test.firebaseio.com/questions")
// Order the questions on their value and get the one that has the random value
ref.queryOrderedByChild("value")
.observeEventType(.ChildAdded, withBlock: {
snapshot in
// Shuffle your array
let shuffledQuestions = GKRandomSource.sharedRandom().arrayByShufflingObjectsInArray(snapshot)
// Store your array somewhere and iterate through it for the duration of your game
})

Answer 4

You could generate random numbers and store each number in an NSArray. However, when you append it to the array you can check if the array already contains that number.
For example:
for _ in 1...10 {
let amountOfQuestions: UInt32 = 40
var intArray: [Int] = []
let randomNumber = Int(arc4random_uniform(amountOfQuestions - 1)) + 1
if intArray.contains(randomNumber) {
repeat {
randomNumber = Int(arc4random_uniform(amountOfQuestions - 1)) + 1
} while intArray.contains(randomNumber)
if !intArray.contains(randomNumber) {
intArray.append(randomNumber)
}
} else {
intArray.append(randomNumber)
}
print(intArray)
}
After that you can make a FireBase request with your uniquely generated integers. I hope I was able to help :).

Answer 5

Create unsorted Array of ten random Int 0..99
var set = Set<Int>()
while set.count < 10 {
let num = Int(arc4random_uniform(100))
set.insert(num)
}
let arr = Array(set)