The supplementary Swift Playground to Swift 101 - let vs var.
Code:
/*:
# Swift 101 - let vs var
https://medium.com/pretty-swifty/swift-101-let-vs-var-915eb9766c64
Explaining the difference between `let` and `var`.
*/
import UIKit
//let variables
let numberOfMonths = 12
//If you uncomment the line below, the Swift compiler will show you an error.
//numberOfMonths = 11
//var variables
var roomTemperature = 21.5
//It gets warmer!
roomTemperature = 23
//Your favourite coffee shop example
//Start of the day
let numberOfChairs = 25
var numberOfCustomers = 0
//Open the shop doors and 5 customers arrive
numberOfCustomers = numberOfCustomers + 5 // The number of customers is now 5. Therefore the numberOfCustomers must be a mutable variable.