O'Reilly logo

Mastering Swift by Jon Hoffman

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Defining constants and variables

Constants and variables must be defined prior to using them. To define a constant, you use the keyword let, and to define a variable, you use the keyword var. The following are some examples of constants and variables:

// Constants
let freezingTemperatureOfWaterCelsius = 0
let speedOfLightKmSec = 300000

// Variables
var currentTemperature = 22
var currentSpeed = 55

We can declare multiple constants or variables in a single line by separating them with a comma. For example, we could shrink the preceding four lines of code down to two lines like this:

// Constants
let freezingTempertureOfWaterCelsius = 0, speedOfLightKmSec = 300000

// Variables
var currentTemperture = 22, currentSpeed = 55

We can change the value of ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required