Collections

Swift provides typed collections such as array, dictionaries, and sets. In Swift, unlike Objective-C, all elements in a collection will have the same type, and we will not be able to change the type of a collection after defining it.

We can define collections as immutable with let and mutable with var, as shown in the following example:

// Arrays and Dictionaries 
var cheeses = ["Brie", "Tete de Moine", "Cambozola", "Camembert"] 
cheeses[2] = "Roquefort" 
var cheeseWinePairs = [ 
    "Brie":"Chardonnay", 
    "Camembert":"Champagne", 
    "Gruyere":"Sauvignon Blanc" 
] 

cheeseWinePairs ["Cheddar"] = "Cabarnet Sauvignon" 
// To create an empty array or dictionary 
let emptyArray = [String]() 
let emptyDictionary = Dictionary<String, Float>() 
cheeses = [] 
cheeseWinePairs = [:] 

The for-in loops can be used to iterate over the items in collections.