This is a Swift 2.0 conversion of Erica Sadun's RandomGenerator from here: http://ericasadun.com/2015/04/24/swift-that-permutation-generator-thing/

RandomGenerator.swift

/*:
**RandomGenerator.swift**

A Swift 2.0-compatible version of Erica Sadun's take on shuffling a
`CollectionType` available here:
http://ericasadun.com/2015/04/24/swift-that-permutation-generator-thing/.
*/

import Foundation

public struct RandomGenerator<C: CollectionType> : GeneratorType, SequenceType {
    private var backingGenerator : PermutationGenerator<C, [C.Index]>
    public init(_ elements : C) {
        var indices = Array(elements.startIndex..<elements.endIndex)
        for index in 0..<indices.count {
            let swapIndex = index + Int(arc4random_uniform(UInt32(indices.count - index)))
            if swapIndex != index {
                swap(&indices[index], &indices[swapIndex])
            }
        }
        backingGenerator = PermutationGenerator(elements: elements, indices: indices)
    }
    public typealias Element = C.Generator.Element
    public typealias Generator = PermutationGenerator<C, [C.Index]>
    public mutating func next() -> Element? {return backingGenerator.next()}
    public func generate() -> PermutationGenerator<C, [C.Index]> {return backingGenerator}
}

let a = "😤😣😨😭😱😷😸😽😾👣🙀👤😓"
let b = "Hello There"
let c = [1, 2, 3, 4, 5, 6, 7, 8, 9]
let d = ["A":"B", "C":"D", "E":"F", "G":"H"]
let e = ["A":1, "B":2, "C":3, "D":4]
var f = Set(1...10)

print(Array(RandomGenerator(a.characters)))
print(Array(RandomGenerator(b.characters)))
print(Array(RandomGenerator(c)))
print(Array(RandomGenerator(d)))
print(Array(RandomGenerator(e)))
print(Array(RandomGenerator(f)))

What do we do for Swift 3.0 if we use PermutationGenerator?