Swiftly

Swift 5.1 references for busy coders

Collection types comparison

Basic example

Arrays let numbers = [1, 2, 3, 4]
Sets let numbers: Set = [1, 2, 3, 4]
Dictionaries let points = ["Ava": 150, "Eve": 275, "Kim": 115]

Example with explicit type annotation

Arrays let numbers: [Int] = [1, 2, 3, 4]
Set let numbers: Set<Int> = [1, 2, 3, 4]
Dictionaries let points: [String: Int] = ["Ava": 150, "Eve": 275, "Kim": 115]

Empty example

Arrays let numbers: [Int] = [] or let numbers = [Int]()
Set let numbers: Set<Int> = [] or let numbers = Set<Int>()
Dictionaries let points: [String: Int] = [] or let points = [String: Int]()

Order

Arrays Arrays are ordered, each element has its own index.
Set Sets are unordered.
Dictionaries Dictionaries are unordered.

Unique values?

Arrays Can have repeating values.
Set May not have repeating values. Each value is unique.
Dictionaries Keys are unique but values can be repeating.