Using an Array to prevent cases from being used?

Question

So I have this,

    func doStuff() {
       //blahblahblah
    }

    var randomNumber = arc4random() % 4
    randomNumber += 1

    switch(randomNumber) {

    case 1:
    doStuff()
    break

    case 2:
    doStuff()
    break

    case 3:
    doStuff()
    break

    case 4:
    doStuff()
    break
    }

Now I need it to do something like this

    func doStuff() {
       //blahblahblah
    }

    var alreadyUsed = [""]

    var randomNumber = arc4random() % 4
    randomNumber += 1

    if randomNumber is not inside alreadyUsed {

    switch(randomNumber) {

    case 1:
    doStuff()
    alreadyUsed.append("1")
    break

    case 2:
    doStuff()
    alreadyUsed.append("2")
    break

    case 3:
    doStuff()
    alreadyUsed.append("3")
    break

    case 4:
    doStuff()
    alreadyUsed.append("4")
    break
    }
    }

Essentially, I am trying to have something that will randomly select a case, then won't select the same case again the next time the function is run. I am using that first chunk of code as a function. After a case has been used in that function, I do not want the function to use it again. I hope this makes sense.

Thanks guys!

EDIT: Though I'd find it more useful, It doesn't even have to be an array, as long as it gets the job done.

Make an array containing the numbers (1..4). [Shuffle it](http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle). Then take each element in turn, as required. — user2864740, May 04 '15 at 03:31
Good idea! The 3rd part of your suggestion is where I still currently have my problem. I'd be able to remove elements from the array, but I'm not sure how to stop the case from being used along with it. May I have an example? Thank you! — adamitude, May 04 '15 at 03:47

score 5 · Accepted Answer · edited May 23 '17 at 11:58

5

var someArray = [1,2,3,4]

let index = Int(arc4random_uniform(UInt32(someArray.count)))
let randomNumber = someArray[index]

someArray.removeAtIndex(index)

This should do what you want.

First you create an array with the available numbers
Let it randomly pick a number for the index
Remove the number in the array

I've changed the conversion of UInt32 to Int because according to this post:

Int(arc4random()) will crash 50% of the time it's executed on a 32-bit platform because a UInt32 won't fit in an Int32

edited May 23 '17 at 11:58

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answered May 04 '15 at 04:16

Eendje

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Thank you! Exactly what I was looking for. People sadly downvoted my question enough times to prevent me from upvoting yours. 5 rep short :( – adamitude May 04 '15 at 23:24
No problem. People are down voting a tad too fast imo. – Eendje May 05 '15 at 06:09

Using an Array to prevent cases from being used?

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