Swift Set to Array

Question

An NSSet can be converted to Array using set allObjects   but there is no such method in the new Set  introduced with Swift 1 2   It can still be done by converting Swift Set to NSSet and use the allObjects   method but that is not optimal

User · Accepted Answer

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]

User · Answer

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 lt S gt    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

User · Answer

call this method and pass your set   func getArrayFromSet set NSSet - gt  NSArray    return set map    String  0         Like This    var letters Set   Set lt String gt  arrayLiteral   test   test      your set print self getArrayFromSet letters

User · Answer

The current answer for Swift 2 x and higher  from the Swift Programming Language guide on Collection Types  seems to be to either iterate over the Set entries like so   for item in myItemSet              Or  to use the  sorted  method   let itemsArray   myItemSet sorted     It seems the Swift designers did not like allObjects as an access mechanism because Sets aren t really ordered  so they wanted to make sure you didn t get out an array without an explicit ordering applied   If you don t want the overhead of sorting and don t care about the order  I usually use the map or flatMap methods which should be a bit quicker to extract an array   let itemsArray   myItemSet map    0     Which will build an array of the type the Set holds  if you need it to be an array of a specific type  say  entitles from a set of managed object relations that are not declared as a typed set  you can do something like   var itemsArray    MyObjectType       if let typedSet   myItemSet as  Set lt MyObjectType gt     itemsArray   typedSet map    0

User · Answer

I created a simple extension that gives you an unsorted Array as a property of Set in Swift 4 0   extension Set       var array   Element            return Array self            If you want a sorted array  you can either add an additional computed property  or modify the existing one to suit your needs   To use this  just call  let array   set array

User · Answer

ADDITION    Swift has no DEFINED ORDER for Set and Dictionary For that reason you should use sorted   method to prevent from getting unexpected results such as your array can be like   a   b   or   b   a   and you do not want this   TO FIX THIS    FOR SETS  var example Set     a   b   c   let makeExampleArray    example sorted    makeExampleArray    Result    a   b   c    Without sorted     It can be     a   b   c   or   b   c   a    or   c   a   b   or   a   c   b   or   b   a   c   or   c   b   a      simple math    3    6

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