In Swift, let let us defines a constant variable. Notice in the example below, it is used to define an instance of the Music class.
import UIKit class Music { var numRock = 10 var numCountry = 20 } let musicGenre = Music() print(musicGenre.numRock) print(musicGenre.numCountry) musicGenre.numCountry = 30 print(musicGenre.numCountry)