Get a random unique element from an Array until all elements have been picked in Swift

Question

I have the following array:

var notebookCovers = [\"cover1\", \"cover2\", \"cover3\", \"cover4\", \"cover4\", \"cover6\", \"cover7\", \"cover8\", \"cover9\"         


        

Answer 1

It is possible with shuffle:

struct AnantShuffler {

    private var collection: Base
    private var index: Base.Index

    public init?(collection: Base) {
        guard !collection.isEmpty else {
            return nil
        }
        self.collection = collection
        self.index = collection.startIndex
    }

    public mutating func next() -> Base.Iterator.Element {
        let result = collection[index]
        collection.formIndex(after: &index)
        if index == collection.endIndex {
            collection.shuffle()
            index = collection.startIndex
        }
        return result
    }
}

fileprivate extension MutableCollection {
    /// Shuffles the contents of this collection.
    mutating func shuffle() {
        let c = count
        guard c > 1 else { return }

        for (firstUnshuffled, unshuffledCount) in zip(indices, stride(from: c, to: 1, by: -1)) {
            let d: Int = numericCast(arc4random_uniform(numericCast(unshuffledCount)))
            let i = index(firstUnshuffled, offsetBy: d)
            swapAt(firstUnshuffled, i)
        }
    }
}

Use:

let shuffler = AnantShuffler(collection: ["c1","c2","c3"].shuffled())
shuffler?.next()