Swift Set to Array

Solution 1:

You can create an array with all elements from a given Swift Set simply with

let array = Array(someSet)

This works because Set conforms to the SequenceType protocol and an Array can be initialized with a sequence. Example:

let mySet = Set(["a", "b", "a"])  // Set<String>
let myArray = Array(mySet)        // Array<String>
print(myArray) // [b, a]

Solution 2:

In the simplest case, with Swift 3, you can use Array's init(_:) initializer to get an Array from a Set. init(_:) has the following declaration:

init<S>(_ s: S) where S : Sequence, Element == S.Iterator.Element

Creates an array containing the elements of a sequence.

Usage:

let stringSet = Set(arrayLiteral: "car", "boat", "car", "bike", "toy")    
let stringArray = Array(stringSet)

print(stringArray)
// may print ["toy", "car", "bike", "boat"]

However, if you also want to perform some operations on each element of your Set while transforming it into an Array, you can use map, flatMap, sort, filter and other functional methods provided by Collection protocol:

let stringSet = Set(["car", "boat", "bike", "toy"])
let stringArray = stringSet.sorted()

print(stringArray)
// will print ["bike", "boat", "car", "toy"]

let stringSet = Set(arrayLiteral: "car", "boat", "car", "bike", "toy") 
let stringArray = stringSet.filter { $0.characters.first != "b" }

print(stringArray)
// may print ["car", "toy"]

let intSet = Set([1, 3, 5, 2]) 
let stringArray = intSet.flatMap { String($0) }

print(stringArray)
// may print ["5", "2", "3", "1"]

let intSet = Set([1, 3, 5, 2])
// alternative to `let intArray = Array(intSet)`
let intArray = intSet.map { $0 }

print(intArray)
// may print [5, 2, 3, 1]