Sets

Set objects are like an unordered Array in which any given value can only be present once.

Their declaration looks as follows:

let set1: Set = [1, 2] 

Note that the Set literal looks like an Array, and so the type must be set explicitly.

The most common Set methods are probably the following:

var set1: Set = ["a", "b"] 
let elementPresent = set1.contains("a")    // true 
let (added1, element1) = set1.insert("c")  // (true, "c") 
let (added2, element2) = set1.insert("c")   // (false, "c") 
let removedElement1 = set1.remove("a")     // "a" 
let removedElement2 = set1.remove("x")     // nil 

Inserting an object that is already in the set leaves the set unaltered, but note that the insert method also returns a tuple containing a Bool of whether the element was added, as well as the element itself.

The remove method returns the object--removed if it was present, or nil if it was not.